Merry Marbling, he's not rlly that quiet but uhm he was a loner bcs he was sick and couldn't attend school
Moreso a happy cheerful silly guy and gloomy serious chill girl.
My little monster - not really a popular guy but he wants to be with his golden retriever attitude and earnestness (also gullible, tragic past, lonely). The girl is a quiet loner nerd that only thinks about school and studying so has the highest grades in the school(kuudere). It takes awhile for them to get together but it's complete.
Its more of a popular guy x loser guy than a loner guy.
Aitsu no daihonmei- BL shounen ai with a rough start gets real slice of life domestic mundanity fluff with dashes OHSHC zaniness and shenanigans after Ch20. Popular handsome cool athletic popular guy and the other guy isn't a loner more of a loser and he only has 2 friends, is ugly, short, has a scar, sucks at english class just low tier or lower mid tier guy overall. Ongoing and only updates yearly or once every two years.
Popular x quiet/loner