Maokin: Joshikou Kyoushi no Ore no Kintama ni Maou ga Yadotta Ken

In the manga's story, a demon lord dwells in Nakata's balls, and if he ejaculates, the demon lord will be unleashed and the world will be destroyed. Nakata is tested to his limit when the students at the all-girls' school where he teaches gets manipulated by magic and try to seduce him. The world's fate now lies on Nakata's shoulders and his balls.

(Source: ANN)