Currently serialized in Shonen Jump+, the hit manga Marriagetoxin—written by Joumyaku and illustrated by Mizuki Yoda—is finally hitting the small screen. The anime adaptation has been making waves since its premiere on April 7, 2026, with online streaming available on Crunchyroll.
The story centers on "Users," individuals who have spent centuries honing the art of assassination. Our protagonist, Hikaru Gero (voiced by Haruki Ishiya), is the heir to the Gero clan, a family of Poison Users which holds top-tier power among the five legendary clans. Despite his lethal skills, Gero is a total amateur in the romance department. His life takes a sharp turn when he meets his latest target: Mei Kinosaki (voiced by Shion Wakayama), a world-class marriage swindler.
To solve his family's succession crisis, Gero strikes an unlikely deal with Kinosaki, who agrees to act as his matchmaker. Can an elite assassin actually find true love? Thus begins the world’s most intense "marriage hunt battle action" starring the ultimate duo: a hitman and a con artist!
To celebrate the broadcast, we sat down with Haruki Ishiya-san, the voice of Hikaru Gero. We discussed his approach to the role, the highlights fans should watch for, and the chemistry he felt with Shion Wakayama-san’s performance as Kinosaki.
Gero: A Character Who "Starts from Zero"
──What were your first impressions when you read the original manga?
Ishiya: I thought the world-building was incredibly unique. I mean, right in the first chapter, there’s a guy being used as a literal chair! (Laughs). Every character is unhinged in some way, yet in this world, everyone treats it like it's perfectly normal. It’s not just the underworld types; even the "normal" people seem to have a screw loose. The potential marriage partners who show up are all pretty out there too, which I found hilarious.
Beyond that, the art is just stunning. Mizuki Yoda-sensei often posts photos of the manuscripts on X (Twitter), and I love seeing the warmth of the hand-drawn lines. The character expressions are fantastic—the girls are cute, the guys are cool, and the darker, more grotesque faces are equally impressive. It’s just a great manga to look at.
──The level of detail in the art really is breathtaking.
Ishiya: I can’t draw at all, so I kept thinking, "Man, it must be so much fun to be able to draw like that!" (Laughs). The coloring is also gorgeous—it has this watercolor-like quality with a vibrant palette. You can see it clearly in Kinosaki’s hair; the gradients are so beautiful that I found myself immediately drawn in.
──That colorful aesthetic really shines in the anime’s key visuals as well. It’s interesting how keywords like "Battle," "Marriage Hunting," and "Hitman" seem totally unrelated, yet they come together perfectly in this series.
Ishiya: At first, I wondered, "How does a hitman do marriage hunting? Does he fight other assassins and find love that way?" But it turns out, saving girls is the marriage hunt! It felt like a really fresh concept. Plus, the story is neatly divided between the battle portions and the date portions.
The date happens right after the battle, and it’s not like the relationship ends once the incident is resolved; it actually continues. The story feels cohesive—every event has meaning. I realized that "Assassins" and "Marriage Hunting" actually have great synergy! (Laughs).
──Definitely (laughs). The structure of having so many different potential partners appear is also quite fun.
Ishiya: Well, if someone saved you like that, you’d fall for them too. Gero really is like a "Prince Charming" in his own way.
──And his specific hitman trait being a "Poison User" is quite the twist.
Ishiya: Exactly! And the poison he uses is actually pretty gruesome. You don’t often see a protagonist who specializes in poison.
──It feels like a "breaking the mold" take on a classic shonen protagonist.
Ishiya: It’s a very solid classic story at its heart. It’s a genuine tale of growth.
──With so many layers to the character, how did you approach the role of Gero?
Ishiya: From the audition stage, I felt that Gero shouldn't start as a "completed" character. For the tape audition, I used it my own interpretation, but during the studio audition, I received a specific direction for one of the lines from the manga: "Try doing this in a totally unhinged way." That really stuck with me.
──"Unhinged"?
Ishiya: The director said, "The manga might be like this, but I want you to try saying it with a bang." At the time, I wasn't entirely sure if I understood it correctly, but apparently, that take was what landed me the role.
I think they were looking for that range—humans have moments where they go off the rails and moments where they are calm. Showing that duality was key. Gero starts off very unstable, but as the story progresses and he survives more life-and-death situations, he grows. Unlike protagonists who are perfect from episode one, Gero is desperate and struggling. I wanted to portray that desperation while slowly uncovering his charm as a human being, using every tool in my acting kit.
──When working on an adaptation, do you usually look at the long-term character arc while recording episode by episode?
Ishiya: Humans have many different faces. I think anime and manga just capture specific moments of a character's life, so I try to imagine the parts that aren't shown on screen.
In Gero's case, he isn't used to girls, so he can't express his charm easily. But when you catch a glimpse of it, he becomes incredibly appealing. I try to act in a way that makes those brief moments feel like steps in his journey toward becoming a better person.
──So the "ratio" of his charm that we see slowly increases?
Ishiya: Right. He’s incredibly sincere. Once he loses that initial sense of desperation and learns to interact with people naturally, I think he’ll go from being accidentally charming to a total lady-killer.
──He really is sincere, isn't he?
Ishiya: He’s a man who literally cannot tell a lie (laughs).
Watch Out for Gero's Heroic Side and The More Sincere, Quiet Moments
──Hearing you talk, it’s clear you enjoy the preparation process for recording.
Ishiya: Hahaha! Well, not as much as I used to. In the past, I’d fill an entire notebook with notes for a single role. But eventually, I realized that a lot of it happens in your head, and there are things you only understand once you get to the studio. If you lock in a direction too strictly, it’s hard to adjust. I found that staying flexible and picking up on what others are doing is more important than over-preparing.
That said, I’ve always loved storytelling—I used to write my own stories—so I definitely enjoy deep-diving into the settings. If I have a chance to talk to the original author, I’ll ask things like, "Is this character this kind of person?" to make sure we're on the same page.
──Speaking with the creator is definitely the best way to be sure.
Ishiya: Of course, for the anime specifically, I talk a lot with Director (Masanori) Hori and the staff about what they want to emphasize. Staying true to the source material is vital, but there are moments where the anime needs to surpass it, and that’s when I try to bring something unique to the table.
──The story follows Hikaru Gero as he teams up with the marriage swindler Kinosaki to solve the Gero family’s succession problem by going on a "marriage hunt." For those about to watch the anime, what aspects of Gero do you want them to look out for?
Ishiya: Combat is where Gero has the most confidence. As a professional hitman, it’s when he shines brightest. Kinosaki’s "marriage hunt plan" involves him saving people using those skills, so that heroic side is his biggest draw early on. I hope viewers find themselves thinking, "Wow, Gero is actually pretty great," right along with the girls he's trying to woo.
I also want people to pay attention to the little things he mutters under his breath. Those are his true feelings coming out, and it’s where his natural charm lies—like when he says, "I don't see it that way," and that one sentence ends up saving someone. That’s just cool.
──A character with a strong core who doesn't get swayed by others is always cool.
Ishiya: Exactly! Also, his expressions change constantly. He’s a hero, but he feels very human. He has his own convictions, but there are moments where his confidence wavers. He’s just overflowing with human appeal.
──He’s very "green" when it comes to girls at the start. Was that fun to play?
Ishiya: It was like looking at myself in middle school! (Laughs). Back then, I had no clue how to talk to girls. Outside of club activities, I spent my school days just sleeping at my desk. Plus, I’m the eldest of four brothers, so the only woman in my life was my mother.
I could talk to girls in early elementary school, but once I hit the later years, I lost all confidence and couldn't speak to them anymore. That lasted until I quit the track team in my second year of high school. I was hopeless.
──It’s hard to know what they're thinking at that age.
Ishiya: But when I decided to become a voice actor in my second year of high school, I realized I had to develop communication skills. I started going to other classrooms during lunch breaks to talk to everyone, boys and girls alike. People thought I had suddenly become a different person, but I’m definitely the type who had to work hard to gain those social skills.
──It’s impressive how logical you were about it—and that you actually executed it.
Ishiya: I felt like I was in a "do or die" situation. I knew I was leaving my hometown anyway, so I just went for it (laughs).
Aiming for "120%" Alongside the Staff
──What was your impression of Shion Wakayama-san’s performance as Kinosaki?
Ishiya: Wakayama-san is someone who has a very clear vision of her performance. On top of that, her energy in the comedic scenes is just incredible.
In the beginning, we talked a lot while building our characters. As the episodes went on, she started anticipating Gero's direction, and I did the same for Kinosaki. Our tempo really improved. At first, it felt like Kinosaki was the one "playing around" at a higher energy level, but eventually, Gero was able to stand beside him as a true partner.
──So you and Wakayama-san really got in sync.
Ishiya: We went out to dinner with the staff once, and we’ve worked together on other sets and stage readings, so we’ve had plenty of time to talk. We often discussed the manga, wondering if Gero and Kinosaki are just partners, or maybe something more.
When it comes to acting, sometimes we discuss how to handle a scene, and other times we purposely don't. Through those interactions, I started being able to "see" how her Kinosaki would react in my head. That’s the power of her acting.
──Wakayama-san mentioned she’s a more "intuitive" actor. What do you think?
Ishiya: Definitely intuitive. When she nails a take, it has that perfect, "instinctual" feel to it.
──In that sense, you two might be a great match.
Ishiya: I think so. I also go into the booth thinking, "I won't know until I try it in the test recording." I think logically beforehand, but I try to throw all that away in front of the mic. In the end, everything comes down to what you receive from your partner, so in that way, we’re similar.
──Actors often say they "think, then discard."
Ishiya: Preparation is important, but unexpected things always happen at the studio. If you just match everyone else, that’s a 100-point performance. But the staff and cast are aiming for 120%. When we’re recording together, it’s vital to pursue those moments of magic that only happen on-site.
──Do you feel that high level of passion from the staff?
Ishiya: I can't hear the directors' discussions in the booth while we're in the studio, but when I see them outside talking about future developments, they look like they're having so much fun. That really boosts our motivation. You can tell they are fans who have read the manga thoroughly and want to make it the best it can be.
──That makes me want to hear the booth conversations too (laughs).
Ishiya: When we look over at the booth from the studio, they all have such serious, focused expressions. I definitely have moments where I wish I could hear what they're saying or see the footage they're looking at.
Speaking of passion, Marriagetoxin studio is a collection of people who love the work and have a clear vision of how they want it to look. You can see that "vision" right in the scripts. I receive a lot of energy just from reading them.
──The first PV was already incredible.
Ishiya: I was so grateful for that. I had just finished a recording session when I saw the footage, and Shion-chan and I were both stunned, like, "Wow, it’s actually moving..." The use of color in the anime is breathtaking, so I really want fans to watch for that!
Watch the first PV here:
──A slightly personal question: in the first episode, Gero screams his true feelings. When do you, Ishiya-san, feel a sense of "small happiness"?
Ishiya: When I’m at home, having a drink while watching anime or playing games (laughs). I’ve always loved adventure and simulation games. When it’s a project I’m in, I usually check it to see how it sounds. Of course, I reflect on my performance, but I also realize, "Wait, I’m actually living the dream I had as a kid."
Game recordings are usually solo, so I don't know how it all fits together until it's finished. Anime is the same—it’s only complete once the art and music are added. Checking the final product is something the "me" from 20 years ago never could have imagined. So, eating something delicious while watching anime or playing a game makes me think, "Ah, this is the life..." (laughs).
──Like, "I actually made my dream come true."
Ishiya: Exactly. "I'm doing it! I'm living the dream!" (laughs). I also get happy when I find a specific cut of animation I love or a perfect music cue.
Also, just going for walks. I like walking at night and stopping by a nice restaurant I’ve never been to. Eating something like tempura makes me think, "Man, I've really become an adult" (laughs).
──Finally, a message for the fans?
Ishiya: This anime is packed with the passion and love from the original creators and the entire anime staff. The cast is constantly talking about the characters, saying things like "I love this part about them!" That energy and love will definitely reach you through the screen.
Marriagetoxin is very easy to get into even for first-time anime-only fans. Please give it a watch and support us!
About "Marriagetoxin"
Synopsis
For hundreds of years, the "Users" have honed the ultimate arts of assassination. Among them, the "Poison Users" of the Five Great Families hold the most absolute power and authority. Hikaru Gero is the young heir to this lethal bloodline. Having spent his life in the shadows of the underworld, he has had zero experience with women—making "marriage" a concept from a different universe.
However, to ensure the Poison User lineage does not die out, the head of the Gero clan issues an ultimatum: Gero’s younger sister will be forced to produce an heir against her will.
Desperate to protect his sister and resolve the succession crisis, Gero encounters his latest target—Mei Kinosaki, a master marriage swindler. Realizing this is his only chance, Gero decides to get married himself and recruits Kinosaki as his coach right then and there.
"That's... the first time anyone has ever proposed to me like that."
With a professional con artist as his advisor, the elite assassin embarks on the most difficult mission of his life: marriage hunting. The curtains rise on the world’s most intense matchmaking battle action, featuring the ultimate assassin-swindler duo!
Cast
Gero Hikaru: Haruki Ishiya
Mei Kinosaki: Shion Wakayama
Kyoko Himekawa: Anna Nagase
Shizuku Ushio: Mariya Ise
Shiori Ureshino: Asaki Yuikawa
Genya Naruko: Soma Saito
Kimie Arashiyama: Hinano Shirahama
Piichi Nakagawa: Shimba Tsuchiya
Akari Gero: Haruka Shiraishi
Toshiki Hanamaki: Isamu Yusen
©Joumyaku, Mizuki Yoda/SHUEISHA, Marriagetoxin Project
© Animate Times
*Some parts of this text have been translated using machine translation
