One thing can be safely said about Chainsaw Man; it's unlike anything you've seen or read before in the world of manga and anime. The manga's transgressive nature makes it hard to categorize. So, is Chainsaw Man shonen or seinen?
Some genre tropes are there, but the manga isn't afraid to shock or disgust - sometimes gratuitously so, according to some; and we expect the anime to be the same.
Is Chainsaw Man Shonen?
Chainsaw Man is a Shonen Jump work and it's available to read online on Shonen Jump's Viz, which is normally home to shonen works.
In short, shonen manga and anime are works marketed towards a young male demographic, especially pre-teens and teenagers.
The term "shonen" describes mostly a demographic and a set of marketing practices, and it doesn't really say much about the content of a manga or anime series.
A shonen work can be fantasy, action, comedy, drama, or a combination of these. Most shonen, however, are at least appropriate for older teens, if not for younger children.
Some readers of Chainsaw Man believe that Shonen Jump isn't the best place for the manga.
While it features a teen protagonist who gains supernatural powers and fights against evil enemies accompanied by a group of other teenagers and young adults, the subject matter is much darker overall.
Aki, a member of Denji's team, starts as the typical shonen rival, being more mature, serious, and competent. His insecurities, emotional vulnerability and personal tragedy make him a deconstruction of this trope, just as Denji had a darker and more miserable life than most naive shonen main characters.
Of course, what makes most people ultimately doubt Chainsaw Man's shonen tag is the amount of gore and sexual content.
A certain degree of violence is to be expected as Denji is a Chainsaw Devil who can transform parts of his body into chainsaws. But this is the least of the show's vulgar content.
Without spoiling much, Chainsaw Man has, on different occasions, depicted group sex, cannibalism, dismemberment, and detailed gore during battles.
Does this make Chainsaw Man a bad show? This is not the case, as it's also a surprisingly funny manga with great characterization and a plot that will make reading through all Chainsaw Man manga volumes a breeze.
It does, however, mean that the manga isn't suitable for children, which might explain concerns over its distribution through a shonen platform.
Is Chainsaw Man Seinen?
Chainsaw Man isn't a seinen manga in that it's not marketed as such. It does, however, have seinen elements.
Despite its young group of main characters, Chainsaw Man is concerned with mature themes, including sexuality and body horror.
Moreover, Chainsaw Man deconstructs several shonen archetypes in terms of both plot and character, showing that it might actually be quite awful if an immature teenager had violent supernatural powers.
Once again, the term seinen describes a demographic - in this case, adult men - a manga or anime is marketed towards, without indicating much content-wise.
Related: Chainsaw Man Part 2 Release Date
This means that it's difficult to categorize a manga as seinen or shonen based on the story and characters alone.
We can, then, conclude that, based on its marketing, Chainsaw Man is a shonen work. It does, however, have elements most often associated with seinen.
It's good for readers to be familiar with Chainsaw Man's more transgressive content to make an informed decision as to whether they or underage people in their care should read it.