Mirai (film) main subject family
Production
Hosoda was partially inspired to write the script for Mirai after seeing his then-three-year-old son's first reactions to having a baby sister in his life. While initially only cautious of the newborn when meeting her for the first time, Hosoda's son threw a tantrum one day, jealous of the attention that his parents were giving his sister. Hosoda's curiosity with how his son reacted, and how he would adapt to being a big brother, prompted him to make the protagonist of Mirai four years old.By making the protagonist so young, Hosoda wanted to capture what life would be like at such a young age. To do this, he brought his own children to the Studio Chizu office so that animators had plenty of reference material to sketch and animate from. Hosoda also wanted to use the fantasy elements of Mirai to propel inner character development, stating, "[...] when the main character meets other people through those elements and changes — it’s not those elements that help him change; it’s really what he feels inside.” Since Mirai was about "how a family can change but always [remained] itself", Hosoda chose to have the film take place in Yokohama, a "city that is constantly changing".Kun's great-grandfather's story was loosely based on Hosoda's wife's great-grandfather, who also worked on warplanes and became injured in wartime conflict.To achieve better authenticity, Hosoda worked with professionals outside of the animation industry to design some of the assets used in the film. Kun's family's house, designed on-screen by Kun's father, was actually designed by real-life architect Makoto Tanijiri. For the sequence where Kun is alone at the train station, Hosoda consulted with Japanese engineer Hideo Shima, designer of Japan's bullet train, to create a model of the shinkansen that was more frightening. In addition, the paper cutouts of strangers that Kun meets were designed by children's book author and illustrator duo Tupera Tupera, whose books his son loves.