Board Thread:Theories and Rumors/@comment-32134097-20181006173818/@comment-3214109-20181015184745

Unless he remembers being scared of her when he was still a baby.

Perhaps Harumi would come back with the Oni? or Sensei Garmadon, who is part Oni, and/or Mistaké would bring her back after seeing her regret her actions and saving that family.