Coffee is a crucial motif in the novel. Kawaguchi makes a point of explaining the relative novelty of this substance in Japan’s history. While Japan has a long history of drinking tea, coffee “was introduced to Japan in the Edo period, around the late seventeenth century” (57). Contrary to the long-held aesthetic appreciation of tea and its rituals, the novel tells the reader that coffee initially “didn’t appeal to Japanese taste buds and it was certainly not thought of as something one drank for enjoyment—which was no wonder, considering it tasted like black, bitter water” (57). Coffee’s bitter, unappetizing qualities make the drink analogous to medicine. As the agent of time travel in the cafe, the novel’s coffee has medicinal applications—for the heart, rather than the physical body. It encourages the time travelers to become better, more wholesome characters whilst providing them with the side effects of nausea and disorientation. The fact that the characters must drink the coffee before it gets cold evokes the imagery of swallowing a bitter pill or unpleasant syrup. But just as foul medicine is necessary for curing ailments, so must the characters drink their coffee, and thus stay in touch with reality.