Before the coffee cools, part two

Overview of the novel The events of the novel take place in a café in Tokyo called "Fonicoli Fonicola" located in a narrow back alley in the city. A unique experiment occurs in this café, manifested by going back in time to the chosen moment within a set of rules. This experience is only available in one seat, and the customer must wait for the ghost sitting on this chair to go to the bathroom. Once time travel occurs, customers cannot leave this seat, and they can only meet people who visited this café in the past. But no matter what happens in the past, it will not affect or change the present. The most important condition of this experiment is that the customer returns to the present before their coffee cools (about an hour).