Mmmh apart from The Third Ending:
https://www.mangago.zone/read-manga/crossing_the_line_1/ for sure (you probably know it already, it's a classic)
And maybe:
https://www.mangago.zone/read-manga/my_bias_appeared/ (another seme that realizes he actually loved the uke and regrets how he acted)
https://www.mangago.zone/read-manga/fair_play_fair_lover/ (kind of? Another cocky playboy seme that catches feelings for the uke and is hurt by the fact that the uke is not as into him as he thought)
https://www.mangago.zone/read-manga/window_beyond_window/ (also kind of? They're childhood friends and it's clear that the uke has always been into him, but I remember the seme regretting not acting sooner when he realizes that the uke slept with someone else while convinced he didn't have a chance)
https://www.mangago.zone/read-manga/fuck_buddy/ (another cocky seme that tries to make the uke jealous but regrets it when it has the opposite effect)
https://www.mangago.zone/read-manga/the_nameless_flower/ (different type of story but 1) same author as Third Ending, 2) seme's pov, 3) regretful seme/chasing arc)
Mother i need more（/TДT)/
LMAOOO if you need more regretful semes I can share my whole list from which I picked the recommendations, although the others are more angsty: https://www.mangago.zone/home/mangalist/2671292/
Its OKAYYYYYYG I FRICKING LOVE ANGST. THANKS GURLLLL ε=ε=(ノ≧∇≦)ノ
Bye girl I'm subscribed to this list for the past few days not knowing you were the same person
AHAHAHAHAHAHAH I'M FAMOUS
This is so Third Ending coded. Does anyone know anymore manhwas with a similar dynamic, preferabally Seme POV too? I always eat this shit up