Ummm I'm not quite sure
But is it perhaps one of these?
https://www.mangago.zone/read-manga/anti_p_t/
https://www.mangago.zone/read-manga/you_and_i_can_t_do_this/
https://www.mangago.zone/read-manga/the_devil_s_temptation/
https://www.mangago.zone/read-manga/the_deputy_wants_to_do_it/
https://www.mangago.zone/read-manga/perfect_buddy/
These are all hate to love tropes, in the office, with a third party involved
Non of theses but thaaanksss
The uke is cute and has to help his family that’s why he was cheap in the office (brown hair)
The seme ( his coworker) is persistent ( dark hair )
And the third party is the uke s hyung he seemed gentle and kind but turned out psycho ( he knew the uke s feeling towards him and there is fourth party a rich guy who likes this hyung ) helppppppp
Looking for a manhwa i forgot the title ( shounen ai or yaoi i can’t remember ( the art was nice)
I remember it started by someone hated a coworker basically because he was cheap and eventually he fall in love with him when he get involved in his life ( and the uke has already a crash on his hyung which appeared nice but at the end of the story was a psycho ..)