18+ Isekai Harem Monogatari

High school student Naoki Oikawa is a chronic masturbator with no purpose in life. After ejaculating on an erotic magazine, he is mysteriously transported to a magical world, where he sees a party of three girls fighting against giant monsters. Naoki's semen holds incredible power, and when enriched by its magic, the struggling maidens slay the beasts with ease.

After taking him to a frontier village, the party members—the soft-spoken priestess Tianne Rutheim, the foul-mouthed elven archer Llusse, and the strong swordswoman Filia Shiora—explain that Naoki is the legendary hero expected to defeat the resurrected demon king, and by consuming the hero's semen, one can enhance their strength substantially. The girls ask Naoki to join them on their quest to save the world, which he happily agrees to. After all, traveling alongside beautiful girls who desire him may not be a bad thing.