Nibi to Kuroba

One day, Nibi, who runs a detective business, ends up interrupting Kuro, a rent boy, at the location where he's on watch. Because of Nibi, Kuro's customer ran away, so he starts clinging to Nibi instead, complaining loudly and causing Nibi to carelessly injure himself. Having one misfortune after another, he was close to giving up on this commission, but Kuro's quick decision saved the day. When he thought it all apparently was settled, Kuro, who seemed to have special circumstances, asked to stay at his house... Under the same roof, Nibi starts living with a rent boy of unknown identity.

(Source: Ichijinsha, translated)