Marriagetoxin (Japanese:マリッジトキシン,Hepburn:Marijjitokishin; stylized asMARRIAGETOXIN) is a Japanesewebmanga series written by Joumyaku and illustrated by Mizuki Yoda. It has been serialized inShueisha'sShōnen Jump+ app and website since April 2022, with its chapters collected in 16tankōbon volumes as of January 2026.Viz Media licensed the series for English release. Ananime television series adaptation produced byBones Film is set to premiere in April 2026.
Hikaru Gero is a young man from the Poison Clan of professional assassins, which has been in existence for hundreds of years. Because he deals in the dark side of society and has never lived a "normal life", he considers himself to have no prospects with women and has no interest in marriage. However, one day, the Poison Clan states that if Gero does not marry and produce an heir to carry on their lineage, they will force his sister into bearing a child against her wishes. Wanting to save his younger sister from such a fate, Gero asks one of his assassination targets to marry him. When thecross-dressing marriage swindler Mei Kinosaki declines, Gero instead has Kinosaki train him to date and how to appeal to women with the goal of finding someone he truly wants to marry.
Gero is the designated heir of the Poison Clan, one of the Five Great Families of assassins. Under pressure to produce an heir to the Poison Clan, he vows to protect Kinosaki in exchange for her help in finding a bride.
Kinosaki is a marriage swindler who has made countless men and women fall for him. Although Kinosaki dresses as a woman and is perceived by others as female, he is actually a guy[4] and claims to be irresistible while dressed as an man.[5]
The Hamster Master, whose family is a branch subordinate to the Beast Clan.
Chinatsu Akakura (赤倉 ちなつ,Akakura Chinatsu)
A "protector" who has skills similar to the assassin clans, but more useful for defense, as they have not specialized. Her weapon of choice is a metal-alloy barrier tape.
Makoto Himi (氷見 マコト,Himi Makoto)
Ureshino's friend, who can change her attitude from meek and mild to aggressive to suit the audience. Her father Yukio has made many sacrifices after the death of her mother.
The Hit Man Hunter, an "ordinary guy" who has great talent with a knife. He wants to open a cafe with his girlfriend Marin and has decided to kill the assassins, starting with the Beast Clan, because he feels his potential patrons would not be able to dine in peace otherwise.
The only daughter of the head of a criminal organization; after he left, he was betrayed by his former colleagues and killed, and they now pursue Erina.
The Kannawa family was thought to have died out before a trio of siblings, led by Kazuma, were hired to capture Erina Zao. He has a sister (Mitsuba) and brother (Kojiro).
Reiji Sakazuki (盃 レイジ,Sakazuki Reiji) (Ghost)
He uses weapons and belongings possessed by ghosts, either forcing humans to attack with cursed weapons or debuffing their abilities with spiritual mementoes.
Marriagetoxin is written by Joumyaku and illustrated by Mizuki Yoda.[7] The manga was officially announced byShueisha on April 11, 2022,[8] and began its weekly serialization for free on theShōnen Jump+ app and website on the 20th of the same month.[9][10] Shueisha also simultaneously publishes the series in English for free on itsManga Plus platform.[11]
In June 2023,Viz Media announced that they licensed the series for English release under the nameMarriage Toxin.[12]
"The Poison Master's Hunt For A Bride" (毒使いの婚活,Doku Tsukai no Kon Katsu)
"Rough Around The Edges" (不束者ですが,Futsutsuka-sha de Suga)
"What Is Charm, Anyway?" (魅力って何?,Miryokutte Nani?)
"Commence Infiltration" (潜入開始,Sen'nyū Kaishi)
"Dreams" (幻覚,Genkaku)
"Thing I'd Be Willing To Trade My Life For" (命懸けても,Inochigakete mo)
Poison Clan Master Hikaru Gero is a killer with morals, targeting only what he calls "human scum", people who have ruined other people's lives; his emotional detachment makes him believe he must remain single, dooming the family line. However, after learning his friend, the Bug Master, has found love, and upon hearing his grandmother is forcing his younger sister Akari to marry against her wishes, he rescues his next target, Mei Kinosaki, rather than killing her. Kinosaki is a marriage swindler who has made countless men and women fall for her, and Gero asks her to help him find a wife. Initially, Gero's lack of personal charisma leads to numerous rejections, but after rescuing Kinosaki from a kidnapper, she realizes his charm lies in his assassin talents, and coaches him to save people as ameet cute. Gero takes a commission to rescue the thief Kyoko Himekawa, who is famous for returning art to its rightful owners; during her latest heist, she was kidnapped. The rescue goes awry when Gero faces Water Master Ushio and a fierce fight ensues.
"Gonna Make Some Fun Music Together" (ド楽しめそう,Do Tanoshime-sō)
"Offering" (捧げ物,Sasagemono)
Bonus Chapter 1
After the mission, Gero and Himekawa go on a date; he relates a story from his childhood, as coached by Kinosaki, and after she reciprocates, he asks to start out as friends. For his next gig, Gero becomes "Daigo Oshima", a bodyguard for Shiori Ureshino, the designated heir to a family party supply company, at the request of her uncle. Ureshino has social anxiety, making an awkward introduction at a college party; she is targeted by Naruko, a Sound Master hitman hired by her aunt. After an attack in the classroom fails, Naruko's next attempt takes place during an off-campus camping trip where Gero shows off his cooking skills and Ureshino charms the other students with close-up magic. Local legends state "Lord Chladni" protected the village from disasters in exchange for child sacrifices; Gero saves Ureshino from a hallucination which would have had fatal consequences at the sacrificial shrine. Although Gero upsets Naruko's hallucinogenic stringed instrument, Naruko makes a realistic "Lord Chladni" giant, convincing the other students to sacrifice Ureshino. In the bonus chapter, Kinosaki explains they dress as a woman because the clothes are more fun, and they would be irresistible as a man.
"The Bug Master's Wedding" (蟲使いの結婚式,Mushi Tsukai no Kekkonshiki)
"Entertainment" (余興,Yokyō)
"Sunset" (夕陽,Yūhi)
"All The Happiness In The World" (100000000幸,100000000 Sachi)
"Hit Man Hunter" (殺し屋狩り,Koroshi Yakari)
"The Meeting" (寄合,Yoriai)
Bonus Chapters 2 & 3
Naruko is defeated by Gero's poison trap and Ureshino uses illusions to dispel "Lord Chladni". She asks her aunt for her help to run the company and then invites Gero for a drink. Kinosaki and Gero attend the wedding of Bug Master Toshiki Hanamaki and Anna Kawakita, where they meet Needle Master Tsunagi and his three sons. During the ceremony, Gero fends off the Puppet Master's minion Yamada, who holds a grudge against Hanamaki, and the Bug Master explains how his branch family is subordinate to the Geros, one of the Five Great Families. After the wedding, Hamster Master Kimie Arashiyama hires Gero to protect her against the "Hit Man Hunter", who has killed the other masters in the Beast Clan. While Arashiyama introduces Gero to the Beast Clan, the Hunter takes Gero by surprise and stabs him. In the bonus chapters, Gero uses a toxin for more fun while Kinosaki singskaraoke, and he prepares abento lunch for Himekawa.
Gero is overwhelmed by Piichi, the Hit Man Hunter, but when Arashiyama leaps to Gero's defense, Piichi stops, saying they are different than the other Masters he had killed before. Piichi has targeted the Beast Clan (led by Toshiro Dogo, head of one of the Five Great Families); after Dogo activates Arashiyama's collar, it starts a three-day countdown to her doom. Approaching the Beast Clan's island, Arashiyama and Gero are split from Piichi and Kinosaki. After Gero defeats the Bird Master, Dogo challenges Gero and reveals his "cross sanguination" program to join strong bloodlines together; the Bird Master revives and adds the abilities of Spear Master Nagihiko Kushima, then collects a sample of Gero's blood before being defeated again. Meanwhile, Dogo's assistant Byakko collects a blood sample from Piichi. After resting and eating a meal prepared by Arashiyama, Gero defeats the Koala Master, but Dogo spirits Arashiyama away during the distraction and Gero is beaten by Dogo's innumerable goons until Water Master Ushio arrives to defend him. In the bonus chapters, Gero goes on a romantic fantasy date with Ureshino and Naruko reveals what is inside his unusually large backpack.
"A Happy, Ordinary Life" (フツーの幸せ,Futsū no Shiawase)
Bonus Chapter 6
Gero and Ushio combine their attacks to defeat the remaining Beast Clan members. Arashiyama has a flashback to her first encounter with Gero, when he rescued her from a failed mission, and calls together rats and hamsters to help her in the present. When Piichi and Kinosaki reach Dogo, Byakko delays them and Dogo transforms Byakko into "frankenbeast" Hyakko, using a bloodline combining 93 Beast Clan branch families. Hyakko beats down Piichi until his spirits are revived by an unexpected call from his girlfriend and he prevails; while Piichi recovers from the fight, Gero and Ushio finally join the others at the hideout. However, Dogo powers up with Hyakko's blood and knocks out the two masters and Piichi; pushed to the limit and realizing that he needs other people to achieve his goal for a happy, ordinary life, Gero reaches a new level. In the bonus chapter, Tsunagi's fear that Gero has a weird wedding gift is allayed when Hanamaki opens it, revealing towels folded as flowers, on Kinosaki's recommendation.
"Romantic Advice with Mei the Love Evangelist" (愛の伝道師メイの恋愛相談会,Ai no Dendoushi Mei no Renai Soudankai)
"The Man from the Branch Family" (次分家の男段階,Bunke no Otoko)
"The Gero Family's Future" (下呂家の将来,Gero-ka no Mirai)
"Foundation" (礎,Ishizue)
Bonus Chapters 7–10
Gero defeats Dogo with a refined poison which cannot be neutralized; in a last-ditch effort, Dogo attacks Kinosaki, but is paralyzed by Arashiyama, who rallies other Beast Clan branch families to control the beast partners in Dogo's blood. Byakko tries to escape with Dogo, but both are seized by a great wolf, the partner of Dogo's sister Tonako, who promises to punish them as the new head of the Beast Clan, then proposes marriage to Gero. During their victorious return, Piichi explains his strength comes from love and Arashiyama confesses she likes Gero but currently is not his equal, vowing to become stronger and win his heart; inspired by the women he has met, Gero also promises to work on himself. He struggles socially while Kinosaki dispenses love advice, but she says he is making steady progress. When Akari warns him about Teruaki Gero, a cousin who was engaged to her, Teruaki poisons the crowd around them and attacks Kinosaki while they visit their younger brother Okuto; during their fight, Teruaki begs Gero to kill him and concentrate on being the head of the Poison Clan, forgetting the distraction of marriage. In the bonus chapters, Himekawa flusters Gero with bikini photos, Ureshino bonds with him over the mangaRopes of Fate, Kinosaki hires Ushio for the fight against Dogo, and Piichi watches a movie with Marin.
"For the Gero Family" (下呂家のために獣,Gero-ka no Tameni)
"Keep Out" (立ち入り禁止,Tachiiri Kinshi)
"The Protector" (護り手,Mamorite)
"Becoming Stronger" (強くなれる,Tsuyoku Nareru)
"Save Her" (手伝ってよ,Tettsudatte yo)
"Excellent Affinity" (相性抜群,Aishō Batsugun)
"The Pinwheel Masters" (風車使い,Kazaguruma Tsukai)
"Partners" (仲間,Kappuru)
"One Shot" (この一撃,Kono Ichigeki)
Gero weathers Teruaki's attacks, proving he has retained his strength, and earns Teruaki's blessing. Gero's next assignment, to drive Erina Zao to safety, accompanied by her charismatic protector Chinatsu Akakura, introduce themselves with a car crash. Zao is being targeted by Namegawa, her father's former criminal associate, who has hired three siblings (Kazuma, Mitsuba, and Kojiro Kannawa) from the Wind-Wheel Clan, previously thought extinct. Erina initially warns Gero not to fall in love with Akakura, but after seeing his abilities, encourages their match. As Erina is about to fly to safety, the Kannawa trio attack and Erina is kidnapped by Namegawa, but Akakura bursts into the compound to rescue her, boosted by Gero's toxin, and Gero stays behind to fight the Wind-Wheel users to facilitate the escape of Erina, Akakura and Kinosaki, but each eventually rejoins Gero to help him.
"Operation Tear Down That Wall!" (心の壁ぶっ壊し大作戦!!,Kokoro no Kabe Bukkowashi Daisakusen!!)
"Only You" (アナタしかいない,Anata Shika Inai)
"Rental Boyfriend" (レンタル彼氏,Rentaru Kareshi)
"Do Whatever I Want" (やりたい放題,Yaritai Hōdai)
"My Daughter's Happiness" (娘の幸せ,Musume no Shiawase)
"Ghost Master" (霊使い,Rei Tsukai)
"Gratin" (グラタン,Guratan)
"Trash" (ゴミカス,Gomikasu)
"One Seriously Nosy Dude" (ド節介,Do Sekkai)
In the past, the Wind Clan declared war on the other specialist assassins, and the Five Great Families allied to wipe them out; Kazuma was saved by the sacrifice of the patriarch of the Wheels Clan. Erina beats Namegawa and the Wind-Wheel Clan take him away. Gero cooks a celebratory meal with Akakura as part of Erina's plan to bring them together, who orders them to share a passionate kiss. Ureshino introduces Gero to her friend Makoto Himi, who asks him to be arental boyfriend to avoid anarranged marriage to Takeo Heiwajima, the son of a member of theNational Diet. While Himi coaches Gero to meet her father Yukio, Heiwajima "marries" her without her consent in a dubious ceremony led by Ghost Master Sakazuki. At the Himi mansion, Sakazuki overpowers Gero and forces a confrontation between Himi and Yukio; he says she has not been grateful for his sacrifices, and she responds she never showed her true emotions to help ease his burden. Although they reconcile, Heiwajima forces her to agree to marry him to save her father's memories. Before the wedding, Naruko helps Gero recover from Sakazuki's debuff.
With Naruko's help, Gero interrupts the wedding and stops Heiwajima from kissing Himi. Heiwajima had chosen Himi as a form of revenge, but is flabbergasted when she apologizes. Sakazuki throws off a shirt laden with debuffs and punches Gero unconscious; Gero is rescued by the spirit that had possessed him before, and she convinces other spirits to ally against Sakazuki. Defeated, his suicide attempt is thwarted by a compassionate Gero. Kinosaki's leaked information results in the downfall of Heiwajima's father. Himi is literally swept off her feet by Gero, and as thanks she takes him to a concert for Naruko's band, Bourgeoizie. Kinosaki teaches Gero about at-home dating strategies, and takes him to a high-end singles mixer to check his progress, where Leo Beppu crashes the party and proposes to her, but she is unmoved by his cliched dating tactics. Gero's latest investigation has led him to Gun Clan chairman Masato Shiragane, who admits the mixer is a ruse to gather extortion victims. Leo fights Gun Clan leader Miyuki, to stop the raid and protect Kinosaki, but Miyuki prevails. In the bonus chapter, Gero goes on a date with Arashiyama to acat cafe.
Ananime television series adaptation was announced on October 1, 2025. It will be produced byBones Film and directed by Motonobu Hori, withseries composition and scripts handled by Kimiko Ueno, characters designed by Kōhei Tokuoka, who will also serve as chief animation director, and music composed by Taisei Iwasaki and Yuma Yamaguchi.[3] The series is set to premiere on April 7, 2026 on the brand newKa-Anival!! programming block onKansai TV,Fuji TV and their affiliates.[41][42][43]Muse Communication licensed the series in Southeast Asia.[44]
The first volume received positive reviews for its art and action sequences.[51][52] Hikaru Gero has been singled out as a "[v]ery relatable lead"[51] with praise aimed at his design and his relationship with the "bubbly and energetic" Mei Kinosaki.[52] Some criticism was aimed at Kinosaki's supporting role in the story rather than being a "fully realized character."[51]
InAnime News Network's year-end retrospective, Lucas DeRuyter wrote that: "Marriagetoxin's attitude towards dating is so healthy, and it was considered a shoo-in for my pick for the best new manga of the year."[53]
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