Aoi Miura was born and raised in Toyama Prefecture. She has an indecisive personality and does not like summer. She was a core member of her high school swim team, but now she works as an assistant at a small architecture office in Tokyo. One summer day, she meets her childhood friend and first love, Akari Serizawa. During their school days, they spent every day together until the night of the fireworks in their third year of high school. That night, Akari suddenly disappeared. Now, Akari has a man named Aoi.