Ore no Level Up ga Okashi! - Dekiru Otoko no Isekai Tensei

Story:

Zalmen is an adventurer who's finally decided to throw in the towel. Putting an end to this chapter in his reincarnated life, he's decided to take all the money he's made up until this point and blow it on the fanciest brothel in town. It's a once-in-a-lifetime chance to be with an expensive woman AND lose his virginity! However, the moment he finishes something rings in his ear, "Fertilization complete. Level up!" What?!!