There's been a GIGANTIC amount of Shonen (exceedingly popular and successful Shonen at that) that centered around primarily older characters with hardly a young kid anywhere in sight. City Hunter was one of Weekly Shonen Jump's most popular series, and it centered around the comedic/hard boiled cases of private investigator Ryo Saeba, along with a large cast of dangerous criminals and femme fatales. Kid characters, not really so much of a factor at all. Fist of the North Star had Lin and Bat, but they were largely fulfilling the C-3PO and R2-D2 "tag along observer" roles: all the other major characters were (decidedly older and weathered looking) men (and the occasional older woman) aged anywhere from their late 20s (at the youngest) and up. And by the end of the series in its last few arcs, there's a big time jump and Lin and Bat end up growing up into full grown adults anyway.FortuneSSJ wrote:One of my problems with GT is how it's a shonen, but most of the main cast feels too old for this genre. I don't think a big part of the audience, especially the young target demographic, feels excited in seeing a shonen filled with old people. The lame casual designs that most characters have don't help. It aged horribly.
It's one of the things Super will always have over GT. The main cast still looks young and fresh, just how a shonen is supposed to be. That charm of having a charismatic cast is something that was lost in GT, so make the adult main character become a kid again was a good idea.
Space Adventure Cobra, almost every single character (major or minor) tends to be 30-something or older. Bastard!! was a gothic medieval fantasy focused on largely all adults with no real prominence of kids anywhere. Similar deal with JoJo's Bizarre Adventure: Stardust Crusaders' Kujo Jotaro is a high school-aged delinquent, but otherwise much of the story is overwhelmingly adult-fixated with most characters ranging from their late 20s/early 30s to middle aged. Rumiko Takahashi's Mermaid Saga largely focused on characters who were ageless and immortal, but were generally frozen somewhere well into their adult years, with one of the few notable child-aged characters in it being a disturbing, homicidal psychopath.
There are countless dozens upon dozens many more examples, but you get the idea. And none of these examples above are any which way obscure either: with the sole exception (among my above examples) of Mermaid Saga, these were all incredibly iconic and best-selling Weekly Shonen Jump mega-franchises.
Generally speaking though, I think the idea that "kids need other kid characters to relate to" is a very silly and dumb idea, and one that's often proven very much incorrect in many cases. With some notable exceptions (Goku and Gohan as kids in DB being a couple) oftentimes kids don't really care about following other child-aged characters, and instead are more interested in adult figures to look up to and aspire to be like. This is especially evident in Western superhero comics where oftentimes kids will find the child sidekick characters lame and tiresome and will instead be more invested in the decidedly adult main hero. But for a long time this kind of sentiment was also plainly and plentifully found in a lot of the Japanese Shonen that was popular and more prevalent up through to the mid/late 90s.
The predisposition for Shonen to fixate on largely and predominantly child or teenage characters is without question much, MUCH more of a millennial thing.