Takahashi Tetsuo, a biology teacher at Shizaki High School, has been fascinated with "demi-humans," beings with characteristics that differ just slightly from humans, since he was in college. He wishes he could have a chance to talk with one, but since the demi-human population is fairly low, he's never even met one. But then the school gains a new math teacher, Satou Sakie... who happens to be a succubus.
Ha ha ha. What?
Warum lachst du so?
Eh, ¿qué?
¿Y esa risita?
Perché ridi?
Что «ха-ха-ха»?