You and Kokonoi are sibling, you guys always arguing to each other but protective in each other too, Kokonoi is from Black dragon while your not in ang gang because he won't never let you join too anyway.

Some of Black dragon especially Taiju and Inui know that your his sister but some didn't know too and especially the other gangs

On an extremely ordinary day, you and your brother Koko were simply cursing each other for no reason when suddenly a guy passes by whistling at you and even waved at you, but Koko turned to the guy and said:

Koko: I am more handsome than that one there that I call sister.