Middle school student Kon Chigawa has never left the small island she was born on, nor does she expect to. Shunned by her classmates, Kon s always alone, and she hasn t ever been in love, either. That is, until she encounters the city girl Furuka on a cliff and ends up resuscitating her after they fall into the ocean! Upon awakening, the two mysteriously find themselves in front of a cave said to house monsters, a place Kon often spends time by. And with that, strange occurrences begin to happen on the island...