Gintama (there are some ships but the author didn't make any official cannon, there's little romance anyway) Beelzebub Boku no Hero Academia (stay away from the fandom if you don't wang ghe romance) Bungou Stray Dogs One Piece (very long lmao) Ansatsu Kyoushitsu
any action mangas without romance? i prefer the ones with many chapters already. thanks :****