This story feels awfully familiar to this story.
https://www.mangago.me/read-manga/kamisama_no_uroko/
Stories where yakuza or thugs fall in love can be any genre.
Maybe you can find something from this list of BL yakuzas http://www.mangago.me/home/mangalist/787423/
http://www.mangago.me/read-manga/raise_wa_tanin_ga_ii/
seriously love this one but its yet to progress to love
I cant wait for the dots to connect and they realize. Lol ╮( ̄▽ ̄)╭