Masquerade Hotel (2019) on Netflix

Plot summary

Three murders have been committed in Tokyo, and beside each victim the killer has left a set of numbers. Kosuke Nitta, the lead investigator on the case, pieces them together and concludes that the next killing is planned for the Hotel Cortesia Tokyo. He goes undercover there as a new front desk employee, cutting his hair and learning the manners the job demands. Naomi Yamagishi, who works the front desk, is put in charge of his training. She teaches him how to serve the guests, and she puts their safety first; he is at the desk to catch a killer, and the two of them work side by side with different aims.