Furachi na Keiji-san

A detective, Issei Takeda, for the sake of destroying a yakuza group, surrenders his body to a yakuza member, Suguru Ishii, in order to obtain insider information. Even though Takeda has a rule where "I refuse to have a lover or a special person," the reason Ishii becomes his lover is...

(Source: Akaneshinsha, translated)