Kai

"Don't forget, we're ninja." - Kai, throughout reaching the climax of the scene.

Kai is the Red Ninja of Fire. His younger sister Nya, who is the mysterious Samurai X. He was chosen to protect the Green Ninja (Lloyd Garmadon) along with the other three Ninja. He is the only ninja known to have a sibling, and the final ninja to unlock his true potential.

Kai's Early Life
Kai, along with his sister, were the children of the blacksmith and owner of Four Weapons. When their father died, Kai took it upon himself to keep the family business going and swore he would become an even greater blacksmith than his father.

Way of the Ninja
When the Four Weapons Blacksmith shop was attacked by Samukai and his Skeleton army, Kai attempted to defend it with some samurai armor he made. The armor was slow and clunky however, and he was soon subdued, and would have died were it not for the quick action of Sensei Wu. Sensei Wu then told Kai about The First Master of Spinjitzu and his two sons who fought over the four Golden Weapons, explaining that a Honest Man had been entrusted with the map to their resting places and the honest man was his father. Sensei Wu took Kai to the Mountains of Impossible Height in order to train him to be a Spinjitzu master so he could save his sister, and all of Ninjago. During his training, Kai had to learn patience and how to harness the "fire" inside of him. This training consisted of running a course before Sensei Wu finished his tea. Kai accomplished this after several days by knocking the teacup out of Sensei's hands when he was about halfway through the course with his wooden training sword. He then told Kai to get some rest, and that his final test would come in the morning.

The Golden Weapon
Later that night, while Kai was pondering Sensei Wu's training and brushing his teeth, he was set upon by three black-suited ninja. Kai was able to fend them off for a while, disorienting them on the training course. Before they could fight much longer, however, Sensei Wu arrived and told them all to stop, at which the three ninjas revealed themselves as more of Wu's students. Wu used Creation to give each of the ninja a suit that matched their elemental properties, and introduced them to each other. He then told them what they needed to do to defeat Lord Garmadon, who is Sensei Wu's brother. Cole interjected and asked if they were still to learn Spinjitzu first. Sensei Wu then informed them that they each already knew it, but it must be unlocked at the right time. Then Sensei Wu said that they would take the horse carriage (pulled by Kai and his fellow Ninja) to the Caves of Despair, the location of the first Golden Weapon, The Scythe of Quakes. At the Caves of Despair, Kai ran ahead of the other ninja while Cole was formulating a plan. The other three ninja chased after him, and caught up to him just before the chamber where the Scythe was housed. Jay then accidentally revealed their position to the skeleton army digging for the weapon, and they were soon in a battle. After Jay discovered the key to unlocking his Spinjitzu, Kai and the others were quick to follow. They used it to drive off the skeleton army, after which they discovered that they had bigger problems, namely, the weapon's guardian, the Earth Dragon. Kai happened to be holding the Scythe at the time, and decided that the only way out was to use it, contrary to Sensei Wu's instructions. After escaping, Kai was strictly repremanded by Sensei Wu, and they went onward toward the next weapon, The Shurikens of Ice.

King of Shadows
While on their way to the Frozen Wasteland, the location of the Shurikens, Wu told the ninja about the most powerful technique in Spinjitzu, the Tornado of Creation. Kai began to attempt it, but was stopped by Sensei Wu, who explained that it could have disastrous concequences if done incorrectly. When the ninja arrived at the location, they discovered several skeleton warriors frozen in ice, and deduced that they had been the second group to arrive there. When they discovered the Shurikens suspended from the ceiling, they lifted Zane up to grab them. When he did, a block of ice formed around him, and the Ice Dragon awoke. The ninja then used Zane as a sled to escape, and went to the hiding place of the Nunchucks of Lightning, the Floating Ruins. On top of the chain, Jay found the Nunchucks, as well as the Lightning Dragon. As they were being chased by skeletons, the ninja used Jay's wing-glider invention to leap off the chain and get away to the Forest of Tranquility. While they were sleeping that night, Kai thought he saw his sister Nya. He got up and chased her to the Fire Temple, where he discovered that it wasn't really Nya, but a shadow deception created by Lord Garmadon. His sister was in the Fire Temple however, only suspended over a pit of lava. Kai had to remove the Sword of Fire from its pedestal to cut the chain and save his sister, which was Garmadon's plan all along. He controlled Kai's shadow, and used it to defeat him. The shadow couldn't be hurt by Kai, but Kai could be hurt by the shadow. Garmadon made multiple copies of the shadow, which made quick work of Kai, and obtained the Sword. All would have been lost if Sensei Wu hadn't intervened at that moment, using his own shadow to defeat Garmadon's Shadow Warriors, regaining the Sword. Garmadon then decided to awaken the Fire Dragon, knowing the guardian would impede the band. The dragon blocked the entrance to the temple, which meant it would be easy for Garmadon to bring the other three weapons to the temple and unite them there, as Samukai had ambushed the other ninjas. Sensei Wu then sacrificed himself to go to The Underworld, in order to keep the weapons apart.

Weapons of Destiny
Kai and Nya discovered that the Dragon only wanted to protect the Sword, and the ninja used the guardians to go to the Underworld to help Sensei Wu. The Dragons performed their variation of Spinjitzu and crossed over, landing not far away from the Skulkin Fortress. They tried to make their way overhead by grabbing onto the roots of plants only to discover that they were spider legs. Out of fear they dropped down to the floor below, where they were noticed by Nuckal. They were going to defeat the Skulkin until the Spiders landed on the stone surface also. Thinking fast, Jay remembered the Tornado of Creation. Although Zane protested about disastrous concequences, they used the Tornado, successfully defeating their enemies. They arrived in the fortress to witness Sensei Wu being defeated by Samukai. Samukai acquired all of the Golden Weapons once but in doing so destroyed his body and transformed him into a portal which Lord Garmadon quickly escaped through. Sensei assured him about Garmadon and the ninja departed the Underworld. Kai and his new friends went back to the Blacksmith shop and were greeted by Nya and several villagers.

Flight of the Dragon Ninja
Cole, Zane, Jay, and Kai were told to train by Sensei Wu, but instead decided to hold a Dragon race. Zane felt that they should be training, in which Kai told him riding your dragon "was kinda training." Kai and the other ninja raced for a while, but Cole won when he "activated the turbo" by throwing food in front of his Dragon's nose. Although he won, Kai said that they'd get him the next day.

The New Masters of Spinjitzu
While Kai and the others were sleeping Nuckal and Kruncha stole his sword in hopes of performing Spinjitzu. They turned on each other though and while they were fighting Kai came out half-asleep and walked by the still pair and turned off the training course that they activated. Believing that the training course turned itself on, Kai yelled to Jay to fix it, but Jay said that he'd "do it tomorrow." When Kai was back asleep the two Skulkin put the weapons back in their places since they couldn't control them.

Return to the Fire Temple
The Fire Dragon, Flame, flew Kai and Nya to the Fire Temple, wanting to show them something. After dismounting the dragon, Flame led Kai to a passage connecting Ninjago to the Underworld. Kai started planning what to do when the ground fell out from beneath him. Krazi alerted Wyplash, who sent several Skulkin after him. He dissarmed his enemies, but they picked him up. Nya and Flame then shot a blast of heat scaring the Skulkin and sealing the passage.

Rise of the Snakes
When reports of Lord Garmadon started surfacing, the Ninja were tasked with going to Jamanakai village to find the source of the problem. They found out it was Lloyd who caused the trouble and tied him to the top of a sign, embarrasing him. When they went back to the Dojo to train Sensei Wu told them to return to Jamanakai village because the Hypnobrai had been released. Jay let Nya fight with them as an "Honorary Ninja." Nya got the Hypnobrai staff to the fountain and healed the bewildered and hypnotized villagers, before the ninja drove the snakes into retreat.

Home
The Ninja were training when they pointed out to Sensei Wu how Zane seemed strange. When the Mailman arrived Kai and the others discovered Zane was orphaned. The next day Kai and the others went to Lloyd's tree-house which acted as a Hypnobrai base. They started destroying it, but a hypnotized Cole turned on them. Before long Sensei Wu came riding in on Flame playing an ancient flute, which cancelled the Serpentine's powers. The group returned to the monastary on Flame right as the Serpentine set it on fire. Zane and Shard put the fire out but, the monastary was beyond repair. Kai and the others verbally attacked Zane but Sensei Wu caught them reminding them that Zane was their team mate and had them apologize. But before they could, Zane flew off on Shard to follow the Falcon. Kai and the others ate around a fire until Nya noticed Zane entering the camp, at which point he led them to there new home, Destiny's Bounty.

Snakebit
After arriving on the Destiny's Bounty, Sensei Wu makes the ninja clean the area. They do and put all the trash and junk in bin outside. However, later Jay's parents, Ed and Edna, arrive to see Jay there. Kai and the other ninjas tease Jay for his parents eccentric behaviors. After some time however, Ed and Edna leave Destiny's Bounty and go back to there home, located in a Junkyard. However, the Serpentine are there and attack Ed and Edna. When the Ninja arrive, they find that they are too late and the Fangpyre had bitten Jay's parents and infected them with venom, transforming them into snake-people. Kai and the other ninja, however, are ambushed by the Fangpyre, who have turned the whole junkyard into a snake infected area. Kai and the others defeat the snakes and leave with Jay's parents. After getting Fangtom's staff, Nya uses it to cure Ed and Edna's venom.

Never Trust a Snake
After arguing about who is the green ninja, Kai and the other ninja are forced to train by Sensei Wu as punishment for arguing and not doing their work. Kai, along with the other ninja, are confused by Sensei Wu's riddle, "What is the best way to defeat an enemy?" Kai fails the riddle along with the other ninja and assume combat is what Wu was talking about. After training and trying to solve the riddle, it is revealed that a boarding school has been attacked by Lloyd and an unknown Serpentine member, later revealed to be Pythor. The Destiny Bounty takes them there, where they drop through the roof of the building. Kai and the others chase the panicking Lloyd through the building until they reach the top of the building. As Lloyd and Pythor reach the roof, Kai and the ninja apprehend Lloyd but Pythor escapes, stealing Lloyd's map. Sensei Wu, however, influences Lloyd to be good while reading a moral to him.

Can of Worms
Kai discovers that Lloyd had deleted all of his high scores on his video game console. However, Lloyd had messed up the other ninja's hobbies as well. Sensei Wu reveals that he put Lloyd up to that to teach the ninja "the destructive power of rumors." After this turn of events, Nya reveals that she has located the Constrictai and Venomari tombs. Kai and Jay take the Venomari tomb while Zane and Cole take the Constrictai tomb. As they arrive, Kai looks around, but is intoxicated with Venomari venom and begins to see elves and gingerbread men attacking him. Jay attempts to protect him while Kai is trembling from the visions. Cole and Zane arrive but are followed by Pythor and the Constrictai. As the two tribes surround them, the ninja believe they will not survive the next attack. Kai hallucinates that a rope is in front of him while he is attacked. Suddenly, Samurai X arrives in a robotic mech and scares away the Serpentine. However, the Samurai knocks them unconscious while the Destiny's Bounty saves them from the Toxic Bogs. Kai's hallucinations then begin to fade.

The Snake King
Kai offered the other ninja a bet whoever finds the identity of the Samurai X, they are the best and the Green Ninja. His attempt to capture the Samurai when he finds her in the Forest of Tranquility and he tries to attack her but the Samurai quickly captures him in a net. Later, when it's his turn to look after Lloyd, he drops him off at an arcade, then leaves, hoping to find the Samurai. After Lloyd has been captured by the snakes, Kai, Cole, Zane, and Jay go looking for him at the Lost City of Ouroboros. The ninja get trapped in a cage that Pythor set up knowing they would come. Pythor puts them up to the challenge of battling Samurai X. The ninja are no match for the Samurai so they do the Tornado of Creation and stop the Samurai. Worried the ninja might win, Pythor tilts the platform, revealing a gigantic hole. When the ninja and the Samurai are about to fall, the Samurai reveals she hasn't really been fighting with them and she will get them out of there, making her suit fly away with the ninja clinging to it. When the suit crashes into the desert, Kai gets thrown farther away from the suit than Cole, Jay, and Zane. Seeing the Samurai also crash near him he goes to investigate. He sees the Samurai take off her head gear and recognizes it as Nya and promises to keep the secret.

Tick Tock
After timing how long Zane could stay underwater Kai and the others go to ask Sensei Wu if they have finally captured their true potential, but find Sensei Wu to be disturbed by something. Kai is corrected, that they have reached full physical potential, but not their true potential. The ninja soon learn of how Lord Garmadon came to be and why it is important to defeat him. Sensei Wu departs while Kai and the others put posters up for Lloyd, who had been captured by the Serpentine. Once the four notice the falcon, they begin to follow it through Ninjago, hoping it will lead them to a Fangblade. After chasing it for miles, the ninja begin to collapse to the ground in exhaustion, Kai finally succumbs to this and allows Zane to follow the Falcon into a snowy woodland. Kai and the others eventually pick themselves up and find Zane to be horrified by something he's uncovered, learning that Zane is an android. Kai and the others still accept him and don't seem bothered by the revelation. After leaving the area, creatures referred to as Treehorns attack the ninja and Kai is defeated by one of the creatures. The queen emerges, but is swiftly frozen by Zane, who gains his true potential. The four of them leave the area and return to the Destiny Bounty to discover Sensei Wu had not returned from his errands.

Once Bitten, Twice Shy
While watching Nya explain the venom process of a Fangpyre, Jay tries to impress her with men's cologne but finds out that Kai and the others pranked him by giving Jay perfume, which Nya is allergic to. The ninja find that a Fangblade is at an amusement park and prepare to go there to acquire it. Jay attempts to go on a date with Nya at the park but Kai warns him not to, telling him "to get his priorities straight." The ninja discover a ride that has Serpentine activity near it. The ninja discover the Serpentine excavating the Fangblade and Kai declares a fight. Kai gains the upper hand in the fight along with the others but a mistake on Zane's part causes them to get frozen from one of his attacks. Kai and the others escape their confinement and Jay is revealed to have gained his true potential while Nya is discovered by all the other ninjas to be Samurai X. Kai brags that he is the first to have found this out but the other ninja ignore his arrogance.

The Royal Blacksmiths
The ninja, upset at losing the Fangblade, brainstorm for where the next Fangblade would be. Cole brings up that he knew about a Blade Cup that seemed to be a Fangblade that his father once won at a talent show. The ninja go to Cole's father and disguise themselves as dancers as to not cause suspicion around Cole's dad. They discover the Blade Cup is located at another talent show and enter it. However, the Serpentine have also discovered the Fangblades location and disguise themselves as people in the audience, judges, and performers. When Kai and the others are ready to perform on stage, they began using various dance moves while the Serpentine attack them on the stage. Kai defends himself from them while Cole defeats the others using a new move. The ninja win the talent show and Cole's father discovers that they have no choice but to steal the blade cup because of the real type of object it is. Pythor attacks and nearly kills Cole's father but Cole protects him and gains his true potential while the Serpentine manage to steal the Fangblade.

The Green Ninja
Sensei Wu returns and surprises them by bringing Lord Garmadon, who has now grown multiple arms. Kai attacks Garmadon but Sensei Wu reveals that he is helping them search for Lloyd and scolds Kai for attacking Garmadon. Kai gets more skeptical about Lord Garmadon and at one point overhears a conversation about the Green Ninja between Nya and Sensei Wu. Kai searches for the Golden Weapons and discovers Garmadon is holding them. Thinking he is stealing them, Kai battles Garmadon and "wins." Sensei Wu however reveals he told Garmadon to fetch the weapons. Kai is dissatisfied to learn that Garmadon allowed himself to be defeated. Kai becomes more and more convinced he is the Green Ninja and believes that only he will gain his true potential when he defeats Lord Garmadon.

After discovering the Fangblade is located at the Fire Temple, the ninja go there to get it and rescue Lloyd from the Serpentine. Garmadon fights his way to Lloyd and rescues him but Pythor still has the Fangblade. In a desperate move, Kai impales the Fangblade to the cave wall with his sword, enraging Pythor. In retaliation, the Constrictai cause the lava to rise in the temple. Lloyd falls onto a rock but the Fangblade begins to fall into the lava. Kai chooses to save Lloyd while the Fangblade falls into the pit below them. Kai gains his true potential and realizes that he wasn't meant to become the Green Ninja but save him to gain his true potential. Lloyd is then revealed as the Green Ninja, destined to defeat Lord Garmadon.

All of Nothing
The episode begins with the ninja cornering Spitta and forcing him to give them information on Pythor's whereabouts. Spitta tells them that they are days behind him. Back aboard Destiny's Bounty, Lloyd suggests that while Pythor is away, they should go to the Serpentine's inner sanctum to retrieve the other three Fangblades. The ninja quickly find the snakes' inner sanctum hidden inside the Constrictai Tomb but Lloyd and Lord Garmadon stay behind. In the inner sanctum, the ninja attempt to defeat the snakes, but to no avail. The ninja are quickly captured and are forced to contact Lloyd for help.

Lloyd and Garmadon get into an arguement and Lloyd gets a message from Nya asking for reinforcements. Lloyd goes on his first mission as the Green Ninja. Kai attempts to escape, but is quickly recaptured by Pythor who now has all four Fangblades. The Serpentine want to celebrate with a Slither Pit tournament, which Pythor agrees to. Lloyd arrives but comically falls down right in front of Pythor. Just before he is captured, however, Garmadon arrives with the Skeleton Army who battle the snakes. Lloyd frees the ninja from their cage, and together they steal the four Fangblades and go back to Destiny's Bounty where Lord Garmadon leaves, making Lloyd upset. The ninja are having a party for Lloyd getting the Fangblades, but little do they know that Pythor is outside their very window, plotting revenge.

The Rise of the Great Devourer
Unaware that Pythor has snuck aboard the Destinies Bounty, the ninja plan to throw the Fangblades into a volcano. This fails when Sensei Wu nearly falls off the deck and is left clinging to the side, only for Kai and the others to save him. Pythor sneaks behind them but Lloyd warns them of his presence. Before Kai and the others can react, Pythor escapes on a Rattlecopter with the Fangblades and takes control over a tour bus. Kai fights off Serpentine on the top of the bus but is nearly knocked onto the road. Eventually Sensei Wu detaches the engine from the rest of the train and confronts Pythor, much to Kai's dismay.

The bus crashes into the Lost City of Ouroboros, halting the ninja's transportation. Fortunately, Lloyd arrives and takes them aboard the Destinies Bounty. Just as Kai and the others attempt to save Sensei Wu, Pythor unleashes the Great Devourer.

The Day of the Great Devourer
After watching his mentor and Pythor get eaten by the Devourer, Kai quickly leads the ninja and their allies back to the Destinies Bounty, but the Devourer follows them and destroys their former home. The team decides to escape to Ed and Edna's junkyard on their vehicles. While their they discover that the Great Devourer has followed them and they use the Tornado of Creation to build a machine out of all the scrap at the junkyard to defend themselves against it, with Kai and Zane piloting near the back. The ninja manage to drive it away from the area but Zane is injured during the conflict.

Realizing the serpent is heading to Ninjago City, Kai and the others follow it to its destination. While the creature begins destroying the city, the ninja arrive and attack it. The fight is interrupted by the ninja's dragons returning, the dragons having gained their true potential as well. Kai and the others cheer their respective dragon on until the Devourer gains the upside of the fight. Lord Garmodon arrives and alerts the ninja that the only way to truly destroy the devourer is to hit its weak spot with the Golden Weapons. Kai is reluctant to hand him the weapons but eventually agrees. Kai and the others lead the snake around the city, eventually trapping it. Kai and the others watch as Garmodon jumps from a building and strikes the creatures head with the weapons, causing it to explode into a mass of green blood. Kai is annoyed that the Golden Weapons are no where to be seen, but rejoices when he discovers that Senei Wu is alive. Victorious, the ninja celebrate.

Appearance
Kai wears a red ninja outfit, and has brown, spiky hair. He will usually have an arrogent expression on his face in battle. His Minifigure also has some scars on its face.

Personality
Kai is very tempestuous, and often leaps into things before he thinks. At the beginning when he first starting training, he was less interested in teamwork and patience, because of his determination on finding his sister, but eventually learned to get along with the other ninja. He is a kind person who cares greatly for his friends and is very protective of his little sister Nya. Other characters have noted he has an inflated ego. Although he may be an "act first-ask questions later" type, he'll come through in a pinch. In the Season Finale, it seems he has matured greatly and encourages the team to keep fighting.thumb|300px|right

Weapons
Kai currently uses the Sword of Fire, but once wielded a normal katana. In his spinner sets, Kai would also use a double bladed dagger, a flail, a Double scythe, a spear, and a Golden katana.

Trivia

 * Sensei Wu recruited Kai last during his search.
 * In the TV show (both seasons), Kai is missing his scar on his right eye.
 * Kai was the last ninja to unlock his true potential, which is highly ironic, due to the fact that he was the first NRG Ninja to ever be publicly released in a set.
 * The name Kai means "Water" in Hawaiian, as opposed to his element, Fire.
 * He has nicknamed his dragon Flame.
 * He is voiced by Vincent Tong.
 * His hair is the only hairpiece that cannot yet be obtained. As it has never appeared in a set, but only his video game variation from LEGO Battles was seen as a genuine LEGO piece.