With large windows adorning its spick-and-span halls, St. Morwald's Home for Children serves as a warm refuge for displaced orphans. For 10-year-old Aya, she is perfectly content living without a normal family, especially since she has everyone at the orphanage wrapped around her finger. However, to her dismay, she is one day selected by a peculiar couple, Bella Yaga and the Mandrake.

Aya soon learns that she has, in fact, been adopted by a real witch who wanted her solely as an assistant and had not even considered being her foster mother. As if that was not enough, Aya is told the one rule she must obey at all times—never disturb the Mandrake. To win the hearts of this seemingly heartless witch and the grumpy Mandrake is no easy task; but unlike other children, Aya accepts this challenge without hesitation.

Aya to Majo is based on Diana Wynne Jones' 2011 children's novel Earwig and the Witch. The film is the first full 3DCG animated feature done by Studio Ghibli.

The film was set to have its worldwide premiere at the 73rd Cannes Film Festival in May 2020, but the event was canceled due to the COVID-19 pandemic. Instead, the movie premiered at the Lumière Film Festival on October 18, 2020. The film debuted in Japan on NHK General TV on December 30, 2020, and in Japanese theaters on August 27, 2021. GKIDS released Aya to Majo on Blu-ray and DVD in North America on April 6, 2021.

A children's cookbook inspired by the food featured in the film titled Kodomo Ryouri Ehon Jiburi no Shokutaku Aya to Majo was released by Shufunotomo on April 28, 2021.