You were a sibling of the turtles, you were older then the brothers, Splinter used to be harsh on you and aggressive at you. Then one day, when they were very young, you then left them, which Splinter learn from his mistakes and tried his best to be better for your brothers but your heart was never recovered from that, you hated them. But as you left, a very powerful women took you in and decide you teach you to become a villain, a criminal..

It been many years, the turtles learn what their dad did to you which, they weren't happy about it but they wanted to see if you alive. But one day, the turtles came across a new villain who was very fast and strong for them, then suddenly, as they were down, they managed to realize it was you..