Isekai Harem Monogatari  

Tales of A Harem in Another World, 異世界ハーレム物語

Naoki Oikawa was a 16-year-old male who had an addiction to masturbation. While engaging in self-pleasure one day, his erotic magazine suddenly began glowing, and he found himself transported into a fantastical world. He encountered three female adventurers named Filia Shiora, Tiane Rutheim, and Llusse, who informed him that the realm was at risk of destruction due to the resurrection of the Demon King. The only way to save it was by utilizing Naoki's unique ability-by donating his semen to the three women, their strength would be amplified exponentially. Despite initial hesitation, Naoki agreed to join the group and embarked on an erotic quest.