At Okagi Castle, Yuuki tells his childhood friend An that his family is moving away. Before they part, he says he wants to date her when he returns sometime in the future. Overcome with uncertainty about how they will feel for each other after such a long separation, An runs off and accidentally finds a portal near the castle entrance. Stepping through it, she lands fifty years into the future. Disoriented, An meets a boy named Kibou and his companion, a friendly robot called Butler-kun. Following his grandmother's advice to help any girl in distress at the park, Kibou decides to show her around the city. As they explore together, An realizes that even though Okagi has changed over the decades, the town still holds a familiar and charming atmosphere.