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In an organization of professional killers called Thanatos, there exists an elite assassin. His skills are such that he reigns supreme over all the others in the organization... And he is also the killer of the protagonist's family. The protagonist swears on his life that one day, he will rise through the ranks of Thanatos and challenge the man who took everything from him. Fighting for the position of No. 1, the curtain rises on a battle fought with blood over blood!