This is the time of summer holidays, and no one is more excited than the secondary school of Karin-Chan. Her childhood friend Sakumi-Satpai returns home from college to visit her! Karin and Sakumi with her younger brother Tatsumi-Friends of childhood. Sakumi did not leave for a long time, but now, when he returned, Karin can really see in it the difference. Just seeing this, the heart of Karin beats faster. Her love has not changed in it. Meanwhile, Tatsumi is the same age as Karin, and is in its class at school. He knows about the obvious attachment of Karin to Sakum, however, what are her feelings? It seems he is very careful about Karin, can he console Karin when Sakuma rejects her? Summer Sakumi begins to see how special karin. Will Karin go to the courage to admit? Will Tatsuy reveal their feelings? Will Sakumi understand how special for him was always Karin?