Koibito wa Oni no Hime summary: I, Hayato, once met an Oni princess when I was young, and I made a promise to marry her when I became eighteen. But after that day, I was predisposed to experiencing ecchi disasters whenever I touch women.  With the cause unknown, I intended to live out my life in high school without ever finding a girlfriend. But on that faithful day, Sakura, the Oni princess grown up, came back as promised. This is the tale of an Oni Princess x High School Boy and the mystery of the ecchi Curse Charm that circles them.