Yuki to Matsu
A country doctor finds a man with his throat slit, bleeding out in the snow, and takes him home. And then they fall super in love and have a ton of sex! And adopt a kid for a while, meet old friends, make some great food, and grow old. No death, but we see them together many years later. I cried. One character is a former prostitute. He'll use this to his advantage at one point (he sleeps with someone to get something even though he's in a relationship), and we also see flashbacks of him with his former lover. He and his current partner are very happy.
Tsumasaki ni Kiss
Prequel to Gravity Eyes Long-time lovers and heirs to rival yakuza groups hit rough waters when one agrees to marriage and the other is pursued by the puppy-like host Kyoya (who will get his own happy ending in Gravity Eyes). Injured over his lover's seeming infidelity, Homura temporarily dates the sweetly persistent Kyoya -- something that set the comments section aflame. I thought it was a totally reasonable move by someone who is heartbroken and devastated, but then I've been heartbroken and devastated. If I'd read this while younger, I might have been mad too.
Neko to Wakagashira
Honto Yajuu
A yakuza and a cop fall in love, minus the regular drama. A lot of head injuries though.
Honto Yajuu x Sukitte Iwasete? Crossover
Yakuza wo Shibatte Ii desu ka
Nights Before Night
Years after the tragic death of his lover, Haru from MODS gets a happy ending with his lover’s younger brother.
Tosca no Inu
two boys who grew up in the same orphanage reunite as rivals of member gangs. absolutely beautiful art, but story didn’t click with me.
Gokusen