Ways of parting
I second "ways of parting"
And here are a few more
Gets betrayed by the guy his crush
https://www.mangago.zone/read-manga/again_1/
Gets mistreated by his boyfriend/fuck buddy
https://www.mangago.zone/read-manga/spreading_you_out/
Just read this one, I don't want to spoil hehe
https://www.mangago.zone/read-manga/into_the_blue_water/
Same as the previous one
https://www.mangago.zone/read-manga/a_room_without_space_side_story_1/
His crush tried to take advantage of him
https://www.mangago.zone/read-manga/arpeggio_on_sea_surface/
Betrayed by his ex boyfriend
https://www.mangago.zone/read-manga/honey_bear/
https://www.mangago.zone/read-manga/an_egocentric_way_of_thinking/
Betrayed by his girlfriend
https://www.mangago.zone/read-manga/nerd_project/
Betrayed by everyone around him
https://www.mangago.zone/read-manga/onward_1/
Umm... Idk what's your definition on "betrayal"
I just added the ones where the mc gets WRONGED by someone he cares about deeply
Sorry if it's not totally accurate
Is there any sad romance where the MC betrayed by their lover (⊙…⊙ ) but the ending is MC get together with other character who truly love mc and always try to keep MC happy. (=・ω・=)
If there's borderline yandere or well mc and the new lover obsessed with each other is a plus (๑•ㅂ•)و✧