During the summer vacation, the main character was taken to a rural island where his aunt lived.
While enjoying the summer vacation, get along with your sister, aunt, and children on the island.
Animated summer vacation RPG.

There is a nostalgic atmosphere somewhere like a certain summer vacation game
On an island where time passes while day and night change,
Fishing, swimming, boating
Gacha-gacha, picking up bottles and looking for cats
Then collect insects and battle at a secret base.
You can spend a boyish summer vacation.

But this game is "secret summer vacation".
An event of Naisho that cannot be written in the picture diary is waiting.
Picking up H books, looking into the bath
Watching a late-night program secretly in the middle of the night,
Mischief to sleeping older sisters and everyone ...