Before daylight Love & After morning love by Fujii mitori (related stories) http://www.mangago.me/r/l_search/?name=Fujii+mitori&page=2
By mishima kazuhiko http://www.mangago.me/read-manga/baby_i_love_you & related stories
http://www.mangago.me/read-manga/doushitemo_furetakunai/ …
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Hi! It’s last year’s post, but if you’re still interested, check them out!
IDK if the stories fit your criteria well..
Any manga where the guy likes someone but thinks he's straight about to give up when the other stsrts dating anotger guy?