Masquerade Hotel (2019) on Netflix

A serial (3) killer leaves a GPS code of his next target with each victim - this time Hotel Cortesia Tokyo. A detective goes undercover as hotel staff - haircut, manners etc.

When three murders occur in Tokyo, aside from the corpse and the crime, the commonality is the placement of numbers next to scene of crime. As such, the lead investigator pieces together enough clues to assume the scene of the next murder. He goes undercover and presents himself at an employee of the hotel. The present hotel employee is placed in charge of the detective's training, but it is clear that they have different priorities. In the meantime, there is a potential crime to prevent and criminal to apprehend.

—aghaemi