OK, so there's only 24 chapters out right now, and I don't usually review series this early, but this one is genuinely impressive, and surprisingly progressive and thoughtful in ways I didn't expect, especially for a Jump+ manga. I don't think I've ever been this excited for a Jump+ series since Jigokuraku.
And this manga certainly comes swinging right out of the gate. It starts a bit scattered, with the premise of a "team-up between a hitman and a marriage swindler" looking like prime, if a bit predictable, romcom action fare, but this series is earnest as all hell. Any other series would have the swindler's sob story revealed to be a hoax, but here the story plays it completely straight -- they really are doing it to earn money for their brother's surgery. Any other series would have played the marriage swindler Kinosaki's propensity for crossdressing as a joke or a point of contention, but other than the initial surprise, the protagonist Gero simply accepts this as a fact, and the story moves on.
For a series about a hitman looking for a marriage partner in order to save his lesbian sister from a loveless marriage, Marriagetoxin is astoundingly good-natured and serious about having its main character build honest, open relationships with other people, whether romantic or otherwise. While Kinosaki proposes putting his skills to use as a bodyguard or hostage rescuer in order to get more girls, the story does a surprising amount to humanize the women he meets, including making them instrumental to their own rescues. And despite Gero clearly looking for a romantic relationship, he treats these women as their own people, always putting their needs first, and actually tries to become friends with them first and foremost.
Seriously, don't be fooled by its premise -- this is just an overall really refreshing and kind series about connecting with other people in the guise of a romcom battle shounen. I sincerely hope that it's doing well in the rankings, since I definitely don't want this series to end anytime soon.