
I haven't read many with this trope but this comes close and it's decent imo. You can try it out
https://www.mangago.zone/read-manga/karasugaoka_don_t_be_shy/

Oh and I dunno if this is gap moe per se, but it's a nice read lol. It's kinda along those lines.
https://www.mangago.zone/read-manga/gokushufudou_the_way_of_the_house_husband/

Sorry if you are getting too many notifs but I keep remembering more and more of these right after I post a reply This one is 100% gap moe. 10/10 good read.
https://www.mangago.zone/read-manga/mr_villain_s_day_off

Basically when a person's appearance or perceived personality does not match their actual personalities or taste in things. For example, a very huge, buff guy liking Sanrio or something. Of course there's nothing weird about that! But kinda unexpected right? That gap in looks and their likes/personality is gap moe! Hence why people find that unexpected side cute.
What does gap moe mean?