In a city somewhere in modern day Japan the protagonist 'Ichigo' is drugged, put in a case and taken to a certain place.
When she wakes up she is somewhere normal people can't enter, 'Cafe Tsukikage', a cafe where people who deal in illegal business gather.

Because it exists in the underworld even the owner and waiter at the cafe are contract killers.
While Ichigo is wary, the owner of the cafe Tsukimi explains that he has accepted a certain request.

"This request isn't a kill contract, it's to protect you. That's why we brought you here. Once we've taken on this request we will definitely protect you."

Because of a certain past trauma Ichigo lost her voice, and with no relatives or place to go she half doubtingly accepts a job as a waitress at the cafe.

"Who on earth is targeting me? And who asked these killers to protect me? What will ... happen to me from now on?"

A story about dealing with various people from the underworld, like contract killers, smugglers, and weapons merchants while solving a multi-layered mystery and chasing after the sealed truth.