After spending their first year of high school in peace and quiet, Haruka and Makoto run into Nagisa, a new student who was a member at a swimming club with them when they were kids.  That swimming club is being torn down, so the three of them sneak in to dig up a time capsule that they buried in the back, which is when they are reunited with Rin, the fourth member of their group who left to study abroad.
We're not little kids anymore.
Wir sind keine kleinen Kinder mehr.
No seremos niños eternamente.
Nadie puede ser un niño eternamente.
Nous ne sommes plus des enfants.
Non si rimane bambini per sempre.
Não somos mais crianças.
Мы уже не дети.