Naoki Oikawa, a 16-year-old, is addicted to masturbation. One day, while pleasuring himself as usual, his erotic magazine begins to glow, and Naoki suddenly finds himself in a fantastic world. He appears among three female adventurers who later introduce themselves as the swordswoman Filia Shiora, the priestess Tiane Rutheim, and the elf Llusse. They explain to Naoki that the world is in danger of destruction due to the resurrection of the Demon King, and the only way to save it is for him to use his special power—feeding his semen to the three girls to exponentially increase their strength. Of course, the young hero agrees to join the party, and his erotic quest begins.