Nezumi no Hatsukoi

Raised to be a fixer by the yakuza, Nezumi has never known love. Then Ao, a normal young man who doesn't know the first thing about Nezumi's sordid lifestyle, walks smack dab into her life. The two fall in love and begin living together, but they cannot escape the clutches of evil closing around them. A tale of first love that toes the line between tender and traumatic, this is the story of Nezumi's first love.

(Source: K Manga)