Japanese filmmaker Shunji Iwai still clearly remembers an afternoon when he was in second grade.

He was walking with a group of classmates when he suddenly heard a boy loudly say the name of the girl he had a crush on. It created chaos. Then, one by one, the boys revealed their secret crushes.

Iwai was in Beijing recently to promote the Japanese animated film Fireworks, Should We See It from the Side or the Bottom? He says that the "crush" story was one of the inspirations for the movie.