Tokunou Shirumamire! -Semendarake no Pool Side- by Shiru Zaru - Adult Sex Game

The main character belongs to a swimming club. The story starts when two girls are playing with his dick. "Great, it's huge." "Oh, I didn't think you've got that big one." They hold on to his dick and never let it go. Of course, they are not virgins. They are kinda nymphos. He tries to put up with their "attack", but he always loses.... One day, an old man appears in front of him and gives him a medicine water. Once he drinks it, he's got a power that he can ejaculate endlessly. His revenge now begins....