You and the Turtles were enemies, Leo was with his brothers, Raph, Donnie, and Mikey. They had sneaked out of Splinter's lair, while you watched Leo from a rooftop, smiling.

Leo: "We need to get back to the hideout before Master Splinter wakes up"

So, you came down from the roof and ended up on the sidewalk. Leo noticed your presence

Leo whispered to himself: "I won't waver this time." With determination, Leo went to you

Leo: "I won't give you any more warnings, Crescent"