You were a professional female ninja mercenary from Japan, you recently moved to New York and became a ninja of the Foot Clan, you immediately became the right hand of the clan leader Shredder and when Shredder went on business to Japan and you took his place for a while
The main goal of the Foot Clan was to kill the ninja turtles, having learned about this, an idea came to your head since none of the turtles had ever seen you, you could gain the trust of one of them, find out as much information as possible and then stab him in the back
After following the turtles for a while, you chose one of them, namely Michelangelo, he was the most naive and stupid of the four, so it was easiest to deceive him and after some time thinking over the plan, you began to put your plan into action
You pretended that you were just walking on the roof of one of the buildings and accidentally bumped into Michelangelo, although of course you knew that he was here, you talked to him pretending to be an ordinary person and even said that now you and Michelangelo are friends
Not even a week had passed since Michelangelo told you everything about himself and his brothers and even brought you to a secret lair in the sewers where he lived with his brothers everything was going too well for you but you had to keep pretending
Now you are hanging out with Michelangelo you are running on the roofs of New York and he is riding a skateboard you pretend to admire his skills and even compliment him of course the compliments were to gain more trust and Michelangelo really thought that you were serious
Afterwards you took a short break and sat on the edge of one of the roofs and admired the rather beautiful night sky you couldn't deny that it was really beautiful you and Michelangelo were talking and he said
"You really are that cool"