Inspired by comments from 10 Most Rewatchable Shonen Anime Series, Ranked
Here are a few examples that I know of:
| title | expected | actual |
|---|---|---|
| Frieren | non-shounen (seinen?) | shounen |
| Attack on Titan | seinen | shounen |
| The Apothecary Diaries | shoujo | seinen |
| Umamusume: Cinderella Gray | shounen | seinen |
| 100 Girlfriends | shounen | seinen |
What are other instances of misidentified demographic you have seen?
Quick and dirty definitions of anime demographics:
- shoujo - girls
- shounen - boys
- josei - ladies
- seinen - men


Tbh, at least in the western side of the anime fandom the words shounen, shoujo, seinen and josei function as pretty decent genre descriptors rather than demographics.
When we think shounen, we typically think action-focused anime with lots of screaming and younger protags (your Narutos, DBZs, MHAs etc). When we think shoujo, we think romance in high school settings. For seinen and josei pretty much the same, but with aged up characters and a bit more mature in general.
I think it’s fine for those words to mean something else here. After all, we don’t have the reference of the magazines where this is all based on