Zetsurin!

A boy named Keisuke has long struggled with recurring incidents in which he unintentionally falls onto girls in awkward positions. One day, an angel named Ririi and a fairy named Chappi appear and inform him that he is a legendary hero whose dormant power has caused these incidents. Upon realizing his role, Keisuke experiences a surge of energy, and a large black gun emerges from his groin area, identified as the holy genital gun, Zetsurin Buster.