在东京的宁静角落,生活着幸福的三口之家。而今,这户人家迎来了新生命。爱撒娇的儿子小君,迎来刚出生的妹妹,他感到父母对自己的爱被妹妹夺走,正在恼怒之时,小君却在庭院中遇到来自“未来”的妹妹,并开启了穿越之旅,在家族之树的时空中,他和“未来”的妹妹一起,与童年的母亲、年轻时代的曾外祖父、甚至未来的自己相遇,在冒险中,小君领悟到不同形式的“家族之爱”。The movie follows a 4-year old boy who is struggling to cope with the arrival of a little sister in the family, until things turn magical. A mysterious garden in the backyard of the boy's home becomes a gateway allowing the child to travel back in time and encounter his mother as a little girl and his great-grandfather as a young man. These fantasy-filled adventures allow the child to change his perspective and help him become the big brother he was meant to be.