A popular Japanese manga series (original title: マリッジ・トキシン, Mariッji Tokishin) written by Joumyaku and illustrated by Mizuki Yoda, serialized in Shōnen Jump+ since 2022. It follows Hikaru Gero, a master poison assassin from a legendary clan, who receives his most perilous mission yet: entering a fake marriage with a yakuza heiress to protect her from threats.

Colloquially, any romantic entanglement that feels lethally complicated, blending love, deception, and high-stakes drama—like a wedding vow laced with arsenic.