Marriage Toxin: Story, Cast and Series Facts

Story and premise

For centuries, the Poison Masters have perfected the art of assassination. Among them, the Gero family stands as one of the five most powerful families of Masters, wielding unmatched skill and influence. Hikaru Gero, heir to this infamous bloodline, has lived his life deep in the shadows of the underworld, far removed from love or marriage.

However, to ensure the Poison Master bloodline does not die out, the head of the Gero family declares that Hikaru's sister will be forced to bear an heir. Soon after, Hikaru crosses paths with Mei Kinosaki, a brilliant marriage swindler who also happens to be his current assassination target. Determined to protect his sister and solve the succession problem himself, Hikaru makes an unexpected request on the spot—asking Mei to help him get married.

"...That's the first time anyone's ever proposed like that."

And so, with the cunning marriage swindler Mei as his advisor, the elite assassin Hikaru sets out on the toughest mission for love. His goal? The ultimate marriage. The most unlikely duo—an assassin and a marriage swindler—take on the world's toughest mission for love!

Series details

• Title: Marriage Toxin
• Format: Animation
• Language: Japanese
• Genres: Action, Anime
• Premiere date: 2026-04-07
• Status in TVmaze: Running
• Network listed by TVmaze: Fuji TV
• Network country: Japan
• Typical episode runtime: 24 minutes
• TVMaze ID: 89979
• TVDB ID: 468734

Cast and credited roles

• Haruki Ishitani — Hikaru Gero
• Shion Wakayama — Mei Shirosaki
• Anna Nagase — Himekawa Kyoko
• Mariya Ise — Tidal droplets
• Asaki Yuikawa — Shiori Ureshino
• Sōma Saitō — Naruko Genya
• Shiratama Tonano — Kimie Arashiyama
• Shimba Tsuchiya — Momoichi Nakagawa
• Kazuyuki Okitsu — Dogo Jushiro
• Ayaka Suwa — White Fox
• Haruka Shiraishi — Gero Akari
• Yusen Yu — Toshiki Hanamaki

Seasons in the TVmaze catalogue

• Season 1: premiered 2026-04-07; final listed air date 2026-06-30; episode order: 13.

Source and licence

Adapted from Marriage Toxin on TVmaze. The synopsis is reproduced as plain text; catalogue facts, cast and season records are selected and reformatted. This adapted text is available under CC BY-SA 4.0, following the TVmaze API licence. Network and web-channel credits identify the service listed in this source; they do not establish current streaming availability.