Usotsuki Jouzu to Banken

Yuuji Samejima spends his days doing nothing but getting into fights, but one day, his fight ended up damaging an expensive car nearby. To pay back the loan for the damages, Samejima accepts the car owner, Shinichi Uotani's offer to become the latter's guard dog. As a collateral for the loan, Samejima also had to accept 3 extra conditions. One of it is to work as a staff at the cafe that Uotani runs. He felt tricked because this was a lot different from what he imagined his job as a "guard dog" would be but...

(Source: Kadokawa, translated)