Eleceed
The World’S Best Engineer
Already read that, any more? I just read the childe, do you know more similar recs?
Immortal days, its free on Iezhin
https://www.mangago.zone/read-manga/brutal_satsujin_kansatsukan_no_kokuhaku/
This got no bromine but it all 4 things you mentioned plus it's one of favorites.
Bromance** damn autocorrect
I have read this too this mofo is one of my favs too
He is soooo crazy cool. I love him but from a distance
Action/horror/thriller/mystery but bromance no flxml romance