Leo Kataoka, 24, remembers watching “Grave of the Fireflies,” Studio Ghibli’s anime about the hardships of a boy and his young sister during World War II, in his ninth-grade civics class.

“It’s not like I think about it all the time, but whenever someone talks about watching a film in school, I always think about ‘Grave of the Fireflies’ — it's vividly in my memories till now,” he says.

Many schools in Japan show the 90-minute anime as educational material to tell the emotionally grueling story of the boy having no means to prevent his sister from starving to death.