Seian

Kai is a reaper who guides the souls of the dead. After collecting ten-thousandth soul, the God of Death, Shainos, offers to grant him one wish. Kai chooses to disappear. However, he is reincarnated as Seian, the wayward second son of Count Shureiton. Now living in the place of Seian, whose life had been completely twisted, what fate awaits Kai from here on?

(Source: Kakao Entertainment, translated)