Virgin Killer Ninpouchou

The manga is set in a certain hidden ninja village. Two elite ninja, Goroumaru and Murasaki, compete fiercely to become the village's next village chief. But when Murasaki uses Goroumaru's virginity as a reason to remove him from candidacy, Goroumaru proudly rises to the challenge to lose his virginity. Yet the challenge only plays into the secret plan of the current village chief.

(Source: Anime News Network)