A four-year-old's jealousy becomes the entire world, and the film never minimizes how real that feeling is to him. The garden opens not to grand spectacle but to quiet moments with versions of his family he's never met, each one teaching him something he didn't know he needed. Hosoda's direction transforms a house and its rooms into the kind of place where growing up and letting people in happen at the same speed, and the score settles into you like memory.

Four-year-old Kun's world shifts the moment his baby sister Mirai arrives home. Suddenly he's no longer the center of his parents' attention, and he resents her for it. Jealousy and confusion consume him until a mysterious garden becomes a gateway to something impossible: encounters with his mother as a little girl and his great-grandfather in his youth, along with an unexpected visitor from the future, a teenage Mirai. Each magical journey changes how Kun sees the people around him. His mother wasn't always the adult dealing with his tantrums, and his great-grandfather was once a young man. Traveling through time with his older sister, Kun uncovers his family's story and slowly learns what it means to be part of a family and a big brother. The film blends adventure, fantasy and gentle comedy with slice-of-life drama about childhood jealousy and sibling bonds, told through the eyes of a small boy.