A Librarian's Motto

Iina and Aruto exhibiting their swimsuits gives way to a divergent concourse over whether Kokoro should be cute or cool extinguished by the arrival of a thunderstorm that threatens to make their vacation plans a moot point; fortunately, the storm blows over and the three sisters are on their way with poor Jun none too pleased to be stuck house-sitting the…

Synopsis excerpt via Kitsu.