In Japanese with English subtitles - One day, Kun's mother brings home a new family member. For the four year old boy, joy quickly turns to disappointment when the little sister, Mirai, replaces him as the centre of attention. Kun can't bring himself to accept her as his sister however things turn magical when, with a mysterious garden as his gateway, he encounters his mother as a little girl and his great-grandfather as a young man, and has a series of surprising adventures with his 'older' sister from the future. These experiences change how he sees the world and help him grow in to the big brother he was meant to be.