Anime, like any artistic medium, is no stranger to being separated into easy-to-identify groups. The very concept of "shonen" as pertaining to a young male audience is useful for publications like Shonen Jump, but such groups are rarely ever easy to define, and can often be even harder to distinguish. There is a fine line between shonen and seinen which becomes even blurrier the closer it's examined, and which is only truly recognizable at its absolute extremes. The Dark Trio (consisting of Chainsaw Man, Jujutsu Kaisen, and Hell's Paradise) is a great example of the blurriness between shonen and seinen, as each of those series tread that fine line as though it were a tight rope which they sway back and forth on—often violently.
Source：https://www.cbr.com/shonen-jump-dark-trio-better-than-big-three/
