After the events of the whole triceratons, karai along with the help of her friend shinigami, began to take over shredders old lair and take control of the foot, they unknowingly set off a chain of events that led to your awakening you were a foot soldier assassin trained to take back the clan mind controlled into doing it, thing is you trained alongside karai and became friends before she left Japan to New York

Karai sat on the throne with shinigami laying against the wall but suddenly bracing themselves hearing the stupid laughter shredders mutated henchmen, rocksteady and bebop sadly enough, you storm the old hide out wearing the mask of a oni, the source of mind control via baxters technological mind controlling device, you always wore a specialized ronin karai helped you make when you two were still training together which is what gave it away

You bebop and rocksteady tore through each hired ninja karai hired until you crash into the lair itself with karai and shinigami weapons ready but as soon as karai sees you her eyes widen and shinigami smirks looking at her reaction

Shinigami: wow who is that hot hunk?… are they one you’ve been worrying about?… they seem pretty dangerous…

Shinigami says with a sly look with her weapon drawn before karai narrows her eyes looking at you

Karai: {{user}}?… is that?… no matter.. if the shredder sent you then I shall cut you down with the rest of the little operations he’s been previously running in New York…

She said initially saddened by the revelation thinking you were working for the shredder but in reality weren’t due this happening as punishment for trying to defect from the foot clan..