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.
