Sent to the Realm of Oni and Dragons, Cole and the others must endure new ways to survive in the world to return home. Cole also looks after a rapidly aging Wu and teaches him some of his old lessons for him to better grow as he regains his memories.
Marooned in the Realm of Oni and Dragons, the Ninja spend a full week in the realm trying to gather supplies. Like Zane, Cole remains calm in the situation and spends most of the time tending to Wu, who has aged further into a child. Cole is relieved that he is getting closer to returning to normal, but worried since he has no memory of his past. As Kai and Zane work on creating a radio to establish communications with Ninjago, Cole takes a hungry Wu out and calls him master. This confuses Wu, who gets impatient. Cole tries to teach Wu one of his own lessons, amusing Jay.
As they travel the realm, Cole notes that he has seen no sign of Oni in the realm, just dragons. Cole hears Wu voice his doubts on being a Ninja before they come across a baby Dragon. After finding the young dragon, Cole notices Wu's fear of dragons and relates that he was afraid of them before but he has seen they are actually friendly. However, a large dragon appears and along with the young one attacks them before Cole and Wu run off. As they are chased by the beasts, Wu questions Cole about his words of friendly dragons as he states he misjudged them and uses his weakened powers to barricade a cave for him and Wu once they reach it and is successful protecting them from harm.
As they hide in the cave, the two find paintings of the Oni and Cole realizes that they are not alone in the new world and Cole wants to tell the others.
They soon manage to find food, but when they return, the two discover their campsite gone and tire tracks left behind. Cole follows Wu's lead when he decides to follow the tracks as that might lead them to their friends.
Following the tracks, Cole and Wu were able to track the Ninja to the Dragon Hunters' camp which they found heavily guarded. When Wu tried to charge in and save his friends, Cole was quick to stop him since they were outnumbered and stated they needed to wait. After Wu used one of his quotes "Don't put off 'till tomorrow what could be done today," Cole asked him if he used his words against him. Wu stated Cole borrowed the words from him after he asked.
Wu made the plan to disguised them and ignored Cole's protests before they infiltrated the arena as their friends were forced to fight a Dragon.
Watching from the audience, Cole and Wu were asked who they were and Cole used his alias "Rocky Dangerbuff" for them to blend in and proclaimed Wu as his son, called "Dangerbuff Jr.". However, he was surprised and dismayed to hear that the Dangerbuff were a real a hunter tribe from one of the hunters and they slip away after the latter called some other Hunters over. Cole is annoyed by Wu's criticism of him with disguises before they reach the lever.
They soon get the other Ninjas' attention, with Zane telling Cole that Wu has to leave, as his mere presence (being a quarter Oni) is making things worse for them. When Wu gets an idea, he and Cole pull a lever that throws a vengestone chain to their friends, which helps the Ninja subdue Slab. When Cole says that may help them before Wu and Cole run off.
Cole goes up to his friends and promises to free them before he is called on by the Hunters. Gathering around the fire, Cole, who was still mistaken as a member of the Dangerbuff tribe, listens to the tales of the Hunters. He learns more about the Iron Baron and his motives, when a mention of the Oni is brought up, Cole asks about them and just as his question is about to be answered, a Dragon appears.
At the weapon, Cole and Wu are ordered to maintain the weapons but "accidentally" knock the other Ninja off the stand. They try to rescue them, but the Ninja are immediately put back into the back of the Dieselnaut by Daddy No Legs.
Now in the back of the vehicle, they are forced to sit back and watch as the Hunters reel in and eventually capture the Wind Dragon.
Cole promises to figure a way out of this situation for the ninja, and the Dragons.
As the Dragon Hunters prepare to cook the Wind Dragon for dinner, Cole and Wu manage to pursuade Daddy No Legs to guard the Ninja. While "guarding" them, they make a plan on escaping before Jay suggests they build a dragon as Cole and the other think he is still insane but Jay told that he remembered what Wu told him the first time he met him and decide to make a mech that looks like a Dragon, which they'll believe is the Firstbourne to help out.
Over the next few days, Cole and Wu build the Dragon with parts smuggled out by hiding them in Dragon dung and get them before disposing of it. As their Dragon was now complete, Cole was hoping to take a test flight, but despite losing weight by cutting sweets, it doesn't work. Wu instead insists he will do it.
Later that night, Wu flew the Dragon mech before a shot from Iron Baron knocks the tail off and the real Firstbourne appeared. As she was firing among the camp, Wu and the Ninja provide a distraction for Kai to free the Dragons before they get out themselves.
The Ninja have made it far from the hunters and they see that Wu has aged into a teenager over night. They ask if he has regained any of his memories and he states he vaguely recalls his childhood. As they talk, Heavy Metal appears and threatens the Ninja with her weapon telling them they are her prisoners now. The Ninja don't respond kindly to this and ready for a fight as the hunter interrogates them on Wu truly being the son of the First Spinjitzu Master. After Kai's mumbles, Cole gets scared when Heavy Metal shoots an arrow at his feet once the hunter states they heard Kai. Wu then stepped forward and revealed it was true and introduced himself to her. Rather than attack, Heavy Metal reveals herself to be Faith and that she is on their side and tells him about his father's armor.
As they continue the journey, Cole tells his master that he can't keep up his charade to Faith for long but Wu tells them to trust his judgment as Cole states he didn't teach the Ninja to take the easy way out. Wu then notices Baron and his Hunters approaching and alerts Cole, who believed he was trying to shift the argument until Wu shows him and they flee the area with the others.
As they escape, they deal with repeated attacks from the Hunters but are able to hold them before dealing with an Ice Dragon, but Faith detains it. Wu also gets rid of the hunter on his and Cole's vehicle with him stating he was taking responsibility, as Cole smirks.
Arriving at the Oni Fortress, the Ninja see the area is abandoned and Faith gets frustrated that Baron lied to her and the hunters when discovering the Oni already vacated the realm centuries ago. Wu is asked about the armor's existence and he admits that he doesn't know it's real as she further descents into rage. As she does so, Wu soon notices something on the fortress' door and has Faith move. When Wu shows that door holds a map to the armor, Cole is happy at this as is everyone else.
When the Ninja woke up, Faith handed them chain guns and they start training by chaining up a rock. When they, and Wu, succeeded, they have Wu ride Stormbringer.
When they stopped to look at their map, they realize the Hunters were following them. They were able to defeat them, but Faith has been captured.
At Wu's pleas, the Ninja go to rescue Faith from the Hunters. She berates them and warns them it was trap but the Hunters appear and capture them.
Cole is later tied to a stand with Kai and Zane, Cole shares banter with the others to keep their spirits up. He explains to Wu of why this is important and they share a laugh. He watches as Faith tells the other Hunters that Baron lied to them about the Oni who have been gone from the realm for centuries and tells them that he possibly killed the Hunters to get Dragonbone Blade. After Baron silences any growing rebellion by asking threatening them, an annoyed Baron hushes his prisoners by turning on the elemental device.
However, the torture causes Wu to regain all of his memories and slightly aged further into an older teenager. Cole watches as Wu breaks free of his bonds and begins to fight Wu with the Dragon Hunters but is knocked aside. He watches as Baron negotiates with Wu who accepts the offer of leading him to the armor to return to Ninjago. Cole, Faith, and the Ninja tell him not to help Baron but he tells them to believe in him.
Cole is left to watch as Wu and Baron leave in search of the armor.
Cole and the others were still stuck on the wooden stakes. After they notice that the other Hunters are arguing down below. While they're distracted, they try to rock their bodies side to side in order to knock the stakes over. Zane remarks that it will not be helpful, but considering they have no other choice, they do it anyway.
The rocking seems to be working, and they cheer. As they do, Jet Jack asks them what they're doing, and she cuts them down. After the Ninja are freed, they are skeptical of the Hunters' intentions and Kai tells them if they plan on eating them to eat Cole first since he is filled with cake as his friends are shocked by this. Cole tries to deny this statement since he hasn't eaten any in a year. However, the Hunters reveal they want the Ninja to defeat Baron as they see Baron was only using them and will become even more dangerous with the armor.
They arrive at a bridge that leads to the armor, and find that it's too late, as the bridge has fallen.
Wu then rides back the Firstbourne out of the nest without any chains, and discovers the Ninja, Faith, and the other Dragon Hunters, who had since turned on Baron in his absence and freed the Ninja. As soon as he lands, he reveals Iron Baron's fate. The Ninja bow to him as Dragon Master, but Wu claims that it is he who should bow to them, as it was they who taught him everything since they arrived in the realm. Cole points out that their job isn't finished, Wu asks the Firstbourne if she will get him and his former students home. She agrees to do so, calling upon four other Dragons for the Ninja to ride. Cole gains the earth dragon Slab as his dragon.
With their work finally finished in the Realm of Oni and Dragons, Cole and the others ride the Dragons out of the realm, and begin their return to Ninjago.
Arriving in Ninjago through a portal forming in the air, Cole, Wu and the Ninja are devastated by the city's state and look for their friends. They don't have to search for long as Nya contacts them and they make it in time to save them from Ultra Violet and her lackeys who are scared off by the dragons. Cole then reunites with his other friends who are happy that he and the others are back.
The Ninja continue fighting against the Colossus, using their Vengestone Harpoons to try and incapacitate it. However, the chains prove to be ineffective, and they eventually run out of them. Kai jumps onto the Colossus and begins binding the chains together even tighter.
The ninja soon run out of chains and wonder what to do, before Firstbourne returns and Wu fires his chain gun at the behemoth. The tides continue to turn in the ninja's favor as their allies return to the city to help defeat the Colossus. Very soon, the Ninja and their allies incapacitate the Colossus using the chains, and it falls to the ground. Once Garmadon loses his power, the Colossus crumbles apart and the ninja are victorious. They then have the Sons of Garmadon arrested before Lloyd arrives with his defeated father and the Ninja celebrate his restored power while Garmadon is arrested.
Several days later, the Ninja clean up the Royal Palace before Wu tells them there's trouble. The Ninja run out of the palace and find a crowd celebrating their victory. During this time, Cole spots a tray of cakes and happily digs in as he craved his favorite snack.