In Fujisawa, Sakuta Azusagawa is in his second year of high school. Blissful days with his girlfriend and upperclassman, Mai Sakurajima, are interrupted by the appearance of his first crush, ...

Finally, the day of Mai's high school graduation has arrived. While Sakuta eagerly waits for his girlfriend, an elementary schooler who looks exactly like her appears before him. Suspicious, and ...