Targeted by Yakuza that Helped

Tanaka Koutarou, a taxi driver who works in the countryside, loves his uneventful life more than anything. One day, he ends up saving a yakuza, Kurokawa Hozumi, whose abdomen was bleeding. A few weeks later, under the guise of attempting to return the favour, Hozumi pins Koutarou down...
"I’ll do my best to entertain you."

(Source: Takeshobo, translated)

Note: Includes the one-shot "Doutei no Ore wo Oshitaoshita no wa Osananajimi deshita".