Kun enjoys a happy childhood until the arrival of his baby sister, Mirai. As the new baby becomes the centre of their parents’ attention, Kun becomes increasingly jealous. Little by little, he withdraws into himself. In the backyard where he likes to take refuge, grows a magical family tree. Kun finds himself suddenly catapulted into a fantastic world where the past and the present mingle and he meets his relatives at various ages throughout their life. There is his mother as a child, his great-grandfather when he was an energetic young man, and his little sister as a teenager. Through these adventures, Kun is able to discover his own story.