Two twins - Haruka and Sora, are going back to their grandfather's house.

The two remember their many visits to the house when they were kids. A while ago, they lost their parents in a car accident prompting the move to their grandfather's house... Nao, their old friend, Ryouhei, Haru's classmate, Akira, a miko at a neighboring shrine, Kazuha, Akira's close friend, and Kozue, the class rep, welcome them.

Nothing has changed. Good memories and a silent atmosphere heal the sadness... However, the peaceful life gradually changes... A secret promise made a long time ago. A lost treasure. The real reason for moving to the town. Feelings long kept a secret. The story now starts under the summer sun...