The Case of Getting Lost in Another World with a Cursed Demon Sword That Makes Me Horny.

Rintarou Itoshiki, an ordinary high school boy, was supposed to be tending to the famous sword "Muramura" passed down through his family, but before he knows it, he has been transported to another world. Furthermore, the true identity of Muramura is that of a cursed sword that forces the user to ejaculate as many times as the number of enemies defeated...!? To return to his original world and to suppress his overflowing hypersexuality, Rintarou decides to form a harem party and conquer dungeons.

(Source: Ichijinsha, translated)