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found about this Manga today, and it has been knocking my legs out from under me. It is absolutely one of the funniest mangas I have read.
It can also handle current topics, references, Drama and action very well without it bogging the other elements down. If there is a critique to be had it is that some things can be a little cliche and stereotypical but it's like the Author knows this and is getting the cliches out of the way quickly to get to the really good stuff sooner.
So this is a recommendation from this humble fan and reviewer.
Hope you
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 Alternative TitlesJapanese: キルアオ More titlesInformationType: Manga
Volumes: 13
Chapters: Unknown
Status: Finished
Published: Apr 17, 2023 to Sep 1, 2025
Theme:
School
Demographic:
Shounen
Serialization:
Shounen Jump (Weekly) Authors:
Fujimaki, Tadatoshi (Story & Art) Statistics Ranked: #159512 2 based on the top manga page. Please note that 'R18+' titles are excluded. Popularity: #2956
Members: 8,232
Favorites: 28 Available AtResources | Reviews
Filtered Results: 9 / 10
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Sep 3, 2025
A solid series, but a rushed ending doesn't help me recommend. The author goes to great lengths to establish what's going on, and why it isn't creepy (which it really needs), and it works! You believe Juzo's motivations immediately and really feel his enthusiasm for learning. As it continues and more battles pop up, it turns to various challenges that are more fitting for a middle school compared to just combat, which is great to mix it up, and introduces a ton of enemies, both in school and out of it.
The classmates are fun and interesting characters, you typically don't see Home Ec students mingling ... 
Aug 11, 2024
So first of all, I'm just happy that Fujimaki finally got another job serialized after that flop golf manga, since he's genuinely a great writer, and this work is proof of that... kinda. First of all, though it may sound like a trending type of plot in the current shonen climate, it's a step ahead of the many... many manga that have given it a try by makin the middle aged assassin not attracted to children, let's start with that. The relationships, the settings, they're all very good and entertaining, it's a series that sets itself apart from the rest. The only downside to this
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Sep 1, 2025
This manga starts off strong with an engaging premise that immediately caught my attention. However, around the midway point, it seemed to lose its spark, and the story felt like it was drifting without clear direction. Luckily, it managed to recover towards the end, where the plot became more gripping and enjoyable again. Unfortunately, the series was cut short just as it was getting interesting, leaving me wanting more. If the entire story had been as engaging as the final stretch, I would have rated it an 8. But since a large portion felt slow and unremarkable, my final score is a 6.
May 28, 2024
I find this manga genuinely enjoyable and intriguing. 😊
The plot is simple and straightforward, providing a satisfying experience without overwhelming the reader with complexity. While the story might not stand out as groundbreaking, it excels in its multidimensional approach by seamlessly blending various genres. This genre mix drives the narrative forward and keeps the reader engaged. The writer’s effort to blend these genres together is commendable, though at times, the narrative only scratches the surface of each genre without fully delving into them. This approach might leave some readers wanting more depth in each specific genre. Despite this minor flaw, the series truly shines in its ... 
Nov 28, 2023
I’m still very much ambivalent about this series and don’t fully understand the push Jump is giving it. The issue that has plagued it so far is that it seems to sample many genres without establishing itself well enough in any.
It has potential as a character driven story with the protagonist’s emotional growth as a middle aged man in a middle grade student’s body providing enough stimulus to keep it engaging, but unfortunately it doesn’t feel the character writing is strong enough to convince me that the character is some 40 something year old, as he often sounds like he’s just some fragile child ... 
Jun 12, 2025
Tentative: 8/10
This is one of the series I’m most hopeful about from the current newer Jump crop. It isn’t anything earth-shattering and the basic premise has been done before, but it is fun and the combination of the characters, situations, and profession make for an engaging mix of elements. It has comedy and enjoyable action, and I’m interested to see where it goes. It’s hard to tell this early in the run and I may change the score later, but my score reflects that for a new manga I think it’s very promising and people should give it a shot. There are a lot of ... 
Sep 8, 2025
A story about a middle aged legendary hitman becoming a middle schooler is, surprisingly wholesome.
The action is good, the story is decent, the characters are great (we get a lot of variety for that I assure you) but most of all it's high school premise and all the stuff other than action is just so hilarious and genuinely fun to read. A Legendary Hitman going back to middle school apparently makes a good premise for a comedy huh. There's nothing much else to say about it. It's good, not mind-blowing but good. If you want a chill read with some slick action panels, this is it. 
Nov 11, 2023
Yet another Spy/Assassin series in Shounen jump, and somehow this one is also pretty solid. Whereas Spy x Family has great slice-of-life with decent action and Sakamoto Days has incredible action with good characterization, Kill Blue is more well-rounded, with pretty good action and pretty good characterization/slice-of-life. The premise sounds somewhat cliche, with a top assassin becoming a child, causing several antics. However, Kill Blue executes this premise well, using it to both for some fun comedy and self-reflection of the protagonist. In between fun battles which often involve the innate awkwardness of a middle-aged man in a child body, we get legitimate introspection from
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