Not that I am crazy about the stories in these games but look at Resident Evil 6 or Yakuza 6. Chris Redfield and Kazuma Kiryu are middle-aged in those. Meaning that Japanese games can have grizzly leads. Even Ada was in her mid-40s in RE6 and remained playable. These characters also aged with the franchise. Japanese films, tv dramas or books don´t default to 10th graders either.
Disney´s Punisher S02 has an 42-year-old lead, Iron-man is in his early 50s, and so on. Yet even teens will absolutely eat that stuff up. The current comic Batman has a 13-year-old biological son and Bat-boi has his own comic(s). Asterix and Obelix look about 40. Micky Maus and Bugs Bunny are grown adults. Etc.

Dragon Ball Z/S and especially the manga/LN version of Boruto have a fairly wide cast, with the grown adults either leading the things or being in the spotlight. Not that any of these are good... Kenshin was 29 in the pilot chapter. Kenshiro in his mid-20s and in his early 30s after the time-jump. Space Cobra is 28. All hugely successful Jump releases, so it can be done even with young adult fiction.
Long story short. The only kids I want in my hard-boiled police or military fiction are proper child soldiers. No 14-year-old platoon leaders who participated in half a dozen campaigns but would never touch alcohol cuz that ain´t legal in Japan under 20. Great morals industry.

It´s not even the kids who kill the basic logic of the so-called "grown-up" manga/anime that star kids. It´s the school settings and how seriously that part is treated. Death Note did it right. Light used the school and university as a cover and those barely showed up. Good. Code Geass though. 😐 Not that Geass did anything else right overall.

That´s the real 10-year challenge! Look at was hot about 10 years ago in the industry and bring a bucket of bleach. Oh, I made a Bleach joke. Or is Bleach itself the joke? Hm.