Boku no Piko 3

Pico and Chico meet a pretty, feminine-looking runaway named Coco who lives in a hideout underneath the subway. Pico slowly begins to fall in love with Coco, causing him to question his feelings for Chico. The situation becomes exacerbated when Pico catches Coco and Chico having relations one night. Eventually, they reconcile, having a threesome atop Tokyo Tower.