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?

Even though life is changing for Koyuki and Konatsu, the Aquarium Club and the little salamander that brought them together will remain a special, immutable link between them in the days ahead. As autumn arrives and Koyuki's graduation looms, Konatsu summons all her courage to confront one lingering doubt--must their friendship end just because their stories are diverging?