Samael, the strongest Abyss demon lord, pretends to be Eileen's useless cowardly fiancé. When her pureblood family and the mafia come for her blood, mocking him as weak, he drops his disguise: the Abyss descends, one flick shatters their killing arrays, and the overprotective demon lord is done playing nice to punish anyone who hurt his fiancée.
