The Studio Ghibli genius has been developing the story for two decades.

Hayao Miyazaki, the Japanese storyteller behind Spirited Away, Princess Monoke and countless other classic animations, is coming out of retirement to turn a 20-year pet project into a full-length animated feature.

In an NHK television special Owaranai Hito Miyazaki Hayao (The Man Who Is Not Done: Hayao Miyazaki) on Sunday, the director said he had been working on Kemushi no Boro (Boro the Caterpillar), a CG short for the Ghibli Museum, since announcing his retirement three years ago.

According to the TV show, Miyazaki wasn’t happy with the way the short film turned out and has proposed expanding it into a feature. The animation is based on a story he’s been developing for about two decades, about a caterpillar that’s so small “it may be easily squished between your fingers.”

Miyazaki said it could take up to five years to finish, meaning he’ll be 80 years old by the time it comes out. The film hasn’t been green-lit yet, but Miyazaki is already planning storyboards. He will also continue making CG shorts for the Ghibli Museum, with the Kemushi no Boro short expected to be finished in a year. [via Gizmodo; Anime News Network]

Behind every great movie by Studio Ghibli there’s a tear-jerking score – explore five of the best in FACT’s guide to composer Joe Hisaishi’s greatest moments, starting with Castle In The Sky.