Ones i've read moto takagi wotaku nukoduke preferably the ML/FL are not in their teens(20+), can be lovers or married, seinen or josei... Thanks
Horimiya - Teens but its one of the better romance mangas (IMHO) so I put it out here Last Game - Completed Male always wanted to compete with her since childhood, it's complete. ReLIFE - (completed) It counts as both adult and teen romance so it's weird to differentiate which one is it. (i think its completed now?) Taishou Otome Otogibanashi - neither is old but they're kind of considered to be wife and husband and its heartwarming story without annoying parts (well at least of what i consider annoying in most mangas) Wotaku ni Koi wa Muzukashii - both adults working together and I think there is an anime adaption of it this season. Idk stopped watching anime a while ago. Bonnouji - both in their 25~ or something like that. (completed) Futari no Renai Shoka - older female, younger male but the male is mature I think it lacked something. (completed) Hitorimi Haduki-san to. - Sister set ups a date between her sister (older like 25 or w/e) and her classmate. Its heartwarming no tragedy no drama not too long. (completed) Sasen mo Warukunai - Soldier retires or something along those lines and gets to marry, its just 7 chapters and it isn;t very memorable since i forgot most of what happened there. so ill just leave it here for w/e (completed) Tokidoki - Its one shot and about teens so it goes against almost everything you asked but damns its good and it's just one chapter so its worth giving it a go.