History Manga / Marriagetoxin

* CentralTheme: There's a shoe for every foot. There's someone out there for everyone. This is illustrated by the story being the quest of finding someone for Gero, after seeing his little sister and his best friend both finding someone, despite the challenges they have.

** In one of the bonus chapters, Gero tries to imagine what Kinosaki would look like if he's not cross-dressing. In the imagination sequence, all the girls flock to him like moths to flame, leaving Gero in the dust.

* CentralTheme: There's a shoe for every foot. There's someone out there for everyone, this is illustrated by the story being the quest of finding someone for Gero, after seeing his little sister and his best friend both finding someone.

* EvilMatriarch: The grandmother of the Poison Clan, aside from leading a family of assassins, is obsessed enough with the continuity of the clan that she threatens to have her lesbian granddaughter forcefully impregnated for the sake of producing a heir.

* MakeItLookLikeAnAccident: Naruko, a Sound User assassin, attempts to kill Gero's client Shiori by using hallucinations to either make her try to kill herself or fall off a cliff, as making it look like an accident or a suicide is better than simply murdering her. Even Gero admits that part of the job for any assassin to keep investigations away from their client, and committing an obvious murder is counterproductive.

* BigBrotherInstinct: Gero is protective of his younger sister. His whole reason for wanting to find a wife despite his initial wish to end the Poison Clan with him is because the clan's matriarch would otherwise force her to leave her girlfriend and produce a heir.
* CharacterDevelopment: Shiori's Arc focuses on her development. When introduced, she's shy, withdrawn, and anxious despite her desire to reach out to others and inherit the family company. Over the course of the story, Gero and Kinosaki encourage her to come out of her shell, ending with her stepping up to save her classmates from committing a murder while under a hypnotic frenzy as well as asking her evil aunt to teach her to become a businesswoman that can take on the family enterprise.

* DepravedBisexual: Subverted. Kinosaki is a crossdressing, bisexual marriage swindler that uses his charms to gather money from his targets. That said, he is doing that out of a need to help his sick brother on an expensive medical treatment, and while he continues to use his charms in both men and women, it comes with the intention of helping Gero.

* FanService: Kinosaki in chapter 2 is shown taking a sexy bath, fully portraying that despite being male, he still has an attractive, lithe body.

* JustLikeRobinHood: Kyoko Himekawa is an art thief that is known for stealing art taken by predatory collectors and returning it to the rightful owners.
* KillTheOnesYouLove: The Sound User Clan is implied to only raise one child at a time. Naruko and his older brother were forced to fight as kids, ending with Naruko killing his own brother, something he is deeply regretful of.

* MakingASplash: Water User Ushio is capable of manipulating water freely, doing things like waterboarding someone by making water stick to their face or even just making words with it.

* NoSocialSkills: Gero was raised to be an assassin, and because of that, he did not do things like go to school or any other socializing and is therefore very awkward around people. Trying to go to a match-making session after hearing that the income is one of the most attractive parts of a man just makes him blurt out his income randomly to people, which makes him come across as boastful. His smiles creep people out and his refusal to eat in restaurants (because he was trained to not eat food served by other people) makes his date leave.

* RomanticWingman: Invoked. Since Kinosaki is a marriage swindler, he's a lot more experienced in the field of romance than Gero could ever be, so Gero enlists his help to find a suitable bride.

* ShrinkingViolet: Shiori. She is extremely shy and worried about other's opinion of her, which causes her to have a hard time connecting with others and making friends.

* WholesomeCrossdresser: Downplayed. Kinosaki is a marriage swindler who cross dresses to make it easier to swindle men, but in a personal level, he seems to be a pretty amiable guy who grows fond of Gero and willing to help him. He keeps crossdressing partly because he thinks he looks cute in women's clothing and partly because he would be so charming as a man, it'd be hard for women to notice Gero, something the latter agrees would be the case.
* TheWisePrince: Gero fits this trope's archetype. Gero is the heir of one of the top Poison Clan families, but is deeply saddened by what is implied to have been a horrific traumatic training process imposed on him and an overall lonely life, resigning himself to never finding someone so he can end the cruelty of his clan. Chapter 23 also shows that people in his position on the clan have immense power over the other sub-families, like the Bug User and Needle User families (up to condemning them to death), but he never abuses it and actually befriends those under him.

* BigBrotherInstinct: Gero is protective of his younger sister. His whole reason for wanting to find a wife despite his initial disinterest is because the clan's matriarch would otherwise force her produce a heir for the Poison Clan.

* CoolBigBro: Both Gero and Kinosaki are loving older brothers willing to put everything in line for their younger siblings. Gero changes his life plan of ending the Poison Clan the moment his sister is threatened, while Kinosaki only turned into a marriage swindler to gather money for his younger brother's medical expenses.
* DepravedBisexual: Subverted. Kinosaki is a crossdressing, bisexual marriage swindler that uses his chamrs to gather money from his targets. That said, he is doing that out of a need to help his sick brother on an expensive medical treatment, and while he continues to use his charms in both men and women, it comes with the intention of helping Gero.

* EvilMatriarch: The grandmother of the Poison Clan, aside from leading a family of assassins, is obsessed enough with the continuity of the clan that she threatens to have her lesbian granddaughter forcefully impregnated for the sake of producing an heir.

* HitmanWithAHeart: Gero not only has a major protective streak for his younger sister, but he also refuses to kill anyone that he doesn't think is a bad person.

* WholesomeCrossdresser: Downplayed. Kinosaki is a marriage swindler who cross dresses to make it easier to swindle men, but in a personal level, he seems to be a pretty amiable guy who grows fond of Gero and willing to help him. He keeps crossdressing partly because he thinks he looks cute in women's clothing and partly because he would be so charming as a man, it'd be hard for women to notice Gero.

* EvilMatriarch: The grandmother of the Poison Clan, aside from leading a family of assassins, is obsessed enough with the continuity of the clan that she threatens to have her granddaughter forcefully impregnated for the sake of producing an heir.

* UnsettlingGenderReveal: The first chapter ends with Kinosaki revealing he is a man, much to Gero's surprise.

''Marriagetoxin'' (マリッジトキシン) is a 2022 Comedy and Action manga with art by Mizuki Yoda and story by Joumyaku.

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* ShrinkingViolet: Shiori. She is extremely shy and worried about other's opinion of her, which causes her to have a time connecting with others and making friends.
* UnsettlingGenderReveal: The first chapter ends with Kinosaki revealing he is a man.

The manga started releasing in the Shonen Jump+ app in April of 2022.

!Tropes

* EvilUncle: Gender-inverted. Shiori Ureshino's aunt believes that she's the rightful heir to the company that Shiori's late father had intended for his daughter and sends assassins to kill the girl. Gero finds himself being hired by the girl's uncle to protect her from her aunt.

* NoSocialSkills: Gero was raised to be an assassin, and because of that, he did not do things like go to school or any other socializing and istherefore very awkward around people. Trying to go to a match-making session after hearing that the income is one of the most attractive parts of a man just makes him blurt out his income randomly to people, which makes him come across as boastful. His smiles creep people out and his refusal to eat in restaurants (because he was trained to not eat food served by other people) makes his date leave.

Hikaru Gero is the young heir to the Poison Clan, a high-ranking clan of assassins that specializes in the use of poison to kill their targets. Uninterested in marriage and relationships, Gero is willing to let the clan die with him, up until the matriarch of the clan threatens that if he won't do it, they will force his little sister to produce an heir instead. Out of options to save her, he asks for the help of his current target: marriage swindler Kinosaki, to get him a wife he can marry.

* ChekhovsBoomerang: Gero's water-absorbing polymer. It's introduced as an item gero uses to make jokes at parties, but it is used to save Ushino from falling off of a cliff, and then again to defeat Naruko.
* CoolBigBro: Both Gero and Kinosaki are loving older brother willing to put everything in line for their smaller siblings. Gero changes his life plan of ending the Poison Clan the moment his sister is threatened while Kinosaki only turned into a marriage swindler to gather money for his younger brother's medical expenses.

* EverybodyWantsTheHermaphrodite: Kinosaki is a very androgynous man who often cross-dresses and presents as female, it is shown he has a very easy time to get both men and women in love with him
* EvilMatriarch: The grandmother of the Poison Clan, aside from leading a family of assassins, is obsessed enough with the continuity of the clan that she is threatening to have her granddaughter forcefully impregnated for the sake of producing an heir.
* JustLikeRobinHood: Kyoko Himekawa is an art thief that is known for stealing art taken by predatory collectors and returning to the rightful owners.
* MakeItLookLikeAnAccident: Naruko, a Sound User assassin, attempts to kill Gero's client Shiori by using hallucinations to either make her try to kill herself or fall off a cliff, as making it look like an accident or a suicide is better than simply murdering her, as it would keep investigations away from his client, who stands to benefit from her death.
* MakingASplash: Water User Ushio is capable of manipulating water freely, making things like waterboarding someone by making water stick to their face or even just making words with it.
* MasterOfIllusion: Naruko is capable to use his sound waves to cause hallucinations in the people he targets. He is capable of making Shiori try to kill herself by causing her to see her dead father, and later causes the group of students camping to see the image of a god to convince them into trying to kill Shiori as a sacrifice.
* NoSocialSkills: Gero was raised to be an assassin, and because of that, he did not do things like go to school or even to kindergarten and is very awkward around people. Trying to go to a match-making session after hearing that the income is one of the most attractive parts of a man just makes him blurt out his income randomly to people, which makes him come across as boastful. His smiles creep people out and his incapacity to eat in restaurants (because he was trained to not eat food served by other people) makes his date leave.
* PragmaticEvil: Downplayed. At the end of the day, Gero recognizes that his focus killing only people he consider human garbage to be more of a way to keep his conscience as clean as possible rather than a genuine desire to eradicate evil from the world.

* RescueRomance: Invoked. Knowing how bad Gero is with normal means of meeting people, Kinosaki makes the plan of having him take jobs that involves protecting or saving women, creating an opportunity to make them see him in his best light: fighting to protect them, which puts his charm in full focus and enhances the chance of them falling for him and accepting marriage.

* JustLikeRobinHood: Kyoko Himekawa is an art thief that is known for stealing art taken by predatory collectors and returning to the rightful honors.

Hikaru Gero is the young heir to the Poison Clan, a clan of assassins that specializes in the use of poison to kill their targets. Uninterested in marriage and relationships, Gero is willing to let the clan die with him, up until the matriarch of the clan threatens that if he won't do it, they will force his little sister to produce an heir instead. Out of options to save her, he asks for the help of his current target: marriage swindler Kinosaki, to get him a wife he can marry.

* ShoutOut: During their practice museum date, when Gero finds the first DIY Candy ever made, he says he feels like the [[Film/TwoThousandOneASpaceOdyssey Neanderthal that found a monolith]].

''Marriagetoxin'' (マリッジトキシン) is a 2022 Action manga with art by Mizuki Yoda and story by Joumyaku.