The story is set in 1955 in Kokuga, Hofu City, Yamaguchi Prefecture.

One thousand years ago it was the site of the ancient capital, Suo no Kuni, and traces of the Heian Period (year 794-1185) are passed down to us in the form of ruins and historical place names.

The protagonist is Shinko, a third grade elementary school student, who was born and raised in one of the town's venerable families. She is a little girl whose characteristic is a strange curl on her forehead (she calls it her "Mai Mai"), and her love for playing in the fields. On the other hand, her secret joy is to imagine and to daydream about the world of one thousand years ago. Her fantasies travel far into the days of the Heian Period...

One day, a girl called Kiiko transfers from Tokyo and enters Shinko's class. This girl from the big city has difficulty feeling at home in this small town, but gradually her friendship with Shinko deepens.

Before long, the two of them become engulfed in a strange incident of one thousand years earlier...?!

The film was nominated for the 4th Asia Pacific Screen Award for Best Animated Feature Film.

Mai Mai Miracle won the 2010 Audience Award for the Best Animated Feature for adults at Anima, the Brussels Animation Film Festival (February 2010 in Belgium). It also won the BETV Award for Best Animated Feature at the same festival. It won the Best Animated Feature Film award in the Jury Prize categories at the Fantasia Film Festival in Montréal, Canada (July 2010). The film won the Excellence Prize for Feature Length Animation at the 2010 Japan Media Arts Festival (the 14th festival edition).