Looking for manga with Romance between characters far apart in age, but in a context that is serious and, possibly, legitimate in their community.

Example: Otoyomegatari

Dear Mine
Soredemo Sekai wa Utsukushii

Not sure what kind of story you'd like so here's what I could think of so far:
Hajimari no Niina
Mahou Tsukai no Yome
Yasashii Sekai no Tsukurikata
Watashi no Shounen
Kawaii Hito
Beast in the Office (has smut tho)
Him & Him & Him (has smut as well, and it's poly)
Boukyaku no Shirushi to Hime (author passed away so, it's incomplete but still good)
Youko x Boku SS
Madam Petit
Kiraide Isasete (not sure if you're okay with yaoi but it's really good)
Meiji Hiiro Kitan
Hana o Meshimase
Shinigamihime no Saikon
Marika-chan to Yasashii Koi no Dorei

Spoilers for some of the ones I've listed:

Yasashii Sekai no Tsukurikata - they meet again years after once the heroine is an adult
Watashi no Shounen - Ending is vague and up to the reader

Koi to Yobu ni wa Kimochi Warui