An assassin learns to date to save his sister from a forced marriage
In short: Hikaru Gero, a lethal operative from a centuries-old clan of killers, faces an ultimatum: marry and produce an heir, or watch his sister be forced into the role. To escape this, he enlists a professional marriage swindler to teach him the art of romance and finding a genuine partner.
Marriagetoxin, a Japanese web manga series created by Joumyaku and illustrated by Mizuki Yoda, explores the intersection of high-stakes criminal life and modern dating. Since its debut in April 2022 on the Shōnen Jump+ platform, the story has expanded into a significant franchise, with 19 volumes published as of October 2026. The narrative centers on Gero, the primary successor to the Poison Clan, which is recognized as one of the Five Great Families of assassins.
The central conflict arises when Gero’s family demands he secure their lineage. Rather than comply with their cold-blooded expectations, Gero chooses to protect his sister, allowing her to maintain her relationship with her girlfriend. His unlikely mentor is Mei Kinosaki, a skilled marriage swindler who operates by manipulating others' romantic interests. Despite Kinosaki’s cross-dressing and perceived femininity, he is male and claims to possess an irresistible charm when presenting as a man. Kinosaki agrees to coach Gero in the nuances of courtship, transforming the assassin’s approach to human connection.
The series has achieved notable success, including an anime adaptation by Bones Film that aired in 2026, with a second season scheduled for January 2027. Beyond the primary duo, the story populates its world with a diverse cast, including protectors, thieves, and members of rival clans like the Beast Clan. These characters often grapple with their own legacies, such as the Beast Clan’s reliance on animal partners or the social stigma surrounding families deemed impure. Through this lens, the manga examines how individuals raised in the shadows attempt to navigate the complexities of normal life, party planning, and the pursuit of peace.
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Sources
- Summary by Intellect · source: Marriagetoxin
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