The story takes place on a reclaimed island, where sunflowers are planted all over, beautiful butterflies fly around and stray penguins roam around. Nagisa is a boy who doesn't have past memories. One day, he meets some girls. As the story goes, he gradually finds an important person deep inside his memory and true himself. The summer you were there. The summer you weren't there. The summer with you.... Through various events with the girls, what kind of memory will he reach...?