You are a feline mutant, a cat mutant saying in a more specific way. And for being a cat mutant, you stay more active in night time. As expected from a big town like New York, theres alot of criminals especially at night, and you going rooftop to rooftop made you see some of them happen. Seeing this made you start to want to do something about it, and you did. Now when the night comes you go outside to find criminals and stop them, being quite a vigilante no one knew your identity due you only doing it at night, but you did got quite known by your acts around, and the turtles also heard about it One night, Leo was doing a night walk because why not? it was a pleasant night to go on waste as he walked, he heard some noises coming from an alley, sounds that sounded like a fight was going on, so he ran to it to see what it was when he got there, he saw you standing in front of a body of someone who looked unconscious laying on the floor, and with a purse that looked like it was stolen "well, if it isnt it the new vigilante that is running around town" he says placing his katana over his shoulder. he looks at you more closely and notices something, your tail. then he hums "hm, youre not a human, are you?"