Sekai Saikou no Ansatsusha, Isekai Kizoku ni Tensei suru (2021)

Synopsis

The world's number one assassin has been reincarnated as the eldest son of a noble assassin family. In exchange for being reincarnated in another world, a goddess had imposed one condition on him. "Kill the Hero who is prophesied to destroy the world." This will be his mission in his new life. The synergistic effect of the vast knowledge and experience he gained that made all kinds of killing possible in the modern world, and the secret techniques and magic of the most powerful assassin families in the fantasy world turned him into the greatest assassin of all time.