When her dad gets a job overseas, Konatsu Amano has to leave the Tokyo life she's always known and relocate to a small seaside town to stay with her aunt. The move also means starting a new school surrounded by complete strangers, and it's a lot to handle for a girl who has trouble with change. But on her first day in her new town, Konatsu is instantly drawn to Koyuki, an older girl who is the sole member of the Aquarium Club. Konatsu's introverted tendencies are hard for her to overcome, but maybe she's found something worth coming out of her shell for?

Konatsu senses that she and Koyuki, the only two members of the Aquarium Club, are connected by loneliness, and she's afraid that her bond with Koyuki is weakening as it gradually changes. When Konatsu's feelings finally erupt, Koyuki resolves to face her head-on, leading to a clash of feelings before the girls can confirm how important they are to each other.