Down and Dirty
https://www.mangago.zone/read-manga/down_and_dirty/
Also LITERALLY THIS -
A Link Between Relationships
https://www.mangago.zone/read-manga/a_link_between_relationships/
https://www.mangago.zone/read-manga/roses_and_champagne/ (the uke is not that clueless tho, but still recommended, of course minus the sa scenes)
https://www.mangago.zone/read-manga/love_history_caused_by_willful_negligence/ (i liked this one a lot)
https://www.mangago.zone/read-manga/my_suha/ (a very possessive seme, and a clueless uke)
https://www.mangago.zone/read-manga/even_if_you_don_t_love_me/ (this is a bit frustrating tho)
https://www.mangago.zone/read-manga/the_sound_of_sugar_cubes/ (i remember the ml being kinda crazy, and the mc is quite naive, but i think this is shounen-ai)
Netkama Punch!!! (this one is so funny, but not much smex scenes).
this is on the top of my head, i'm not sure if everything perfectly fits tho, i blame my poor memory if it's not hahhaa. Hope you can check some of this out, and have fun reading :)
girlie this is a manga BUT IT FITS PERFECTLY!! like to the dot its exactly what u described. & the art is super nice too
https://www.mangago.zone/read-manga/ibara_no_naka_no_hana/
alsoo if u like it there's another manga by the same author w the same trope!!
Seme who acts calm or sweet but in the background does everything in his power to keep the uke in his life. Everyone else in the story is scared of how obsessive the seme is but the uke is clueless to it. SMUT IS A MUST!