Viewfinder, honto yajuu, saezuru tori wa habatakani, kobi no kyoujin, but they are all well know, and im sure you had read them. You should try looking for more with tag!
http://www.mangago.me/read-manga/saezuru_tori_wa_habatakanai/
best Yakuza story ever EVER
http://www.mangago.me/read-manga/usagi_otoko_tora_otoko/
this really cute
http://www.mangago.me/read-manga/koi_made_hyakurin/
this another fav
All yaoi yakuza stories. hopefully not already mentioned. http://www.mangago.me/read-manga/ake_nure_goyou_ni_furu_yuki_wa/
http://www.mangago.me/read-manga/boku_no_shiru_anata_no_hanashi/
http://www.mangago.me/read-manga/heart_strings/
http://www.mangago.me/read-manga/kyou_hana_no_gotoshi/
http://www.mangago.me/read-manga/trigger/
http://www.mangago.me/read-manga/zettai_unmei_houteishiki/ 1st in a series.
http://www.mangago.me/read-manga/tsumasaki_ni_kiss/. 2nd.
http://www.mangago.me/read-manga/gravity_eyes/. And spin off.
http://www.mangago.me/read-manga/negai_kanae_tamae/
http://www.mangago.me/read-manga/sugar_code/
http://www.mangago.me/read-manga/nights/
http://www.mangago.me/read-manga/gives/
http://www.mangago.me/read-manga/never_let_go/
http://www.mangago.me/read-manga/narippanashi_no_ai_no_kane/
No one mentioned this awesomeness? :O
http://www.mangago.me/read-manga/yondaime_ooyamato_tatsuyuki/
Tightrope and Totally Captivated
Yaaaay. I haven't read it yet so hesitated about sharing it!! Hehe!
Whaaaaat you still haven't read it yet? :O What are you waiting for? >.<
I don't know... (⊙…⊙ )
Is there any manga with yazuka guys?