CoCo

CoCo is a feminine looking boy with long black hair, who Pico initially believes to be a girl. CoCo has sexual relations with both Pico and Chico. After inadvertently causing some friction in their relationship, CoCo decides to distance himself from Pico and Chico, though they find him again at Tokyo Tower. Little is known of him, but he appears to be some sort of spirit. He is also the main uke of the three, but this can be reversed.

(Source: Wikipedia)