Following the death of her father Kazuo, Momo Miyaura and her mother Ikuko travel from Tokyo to the Seto Inland Sea. Momo carries Kazuo's unfinished letter, which contains only the words "Dear Momo." The two arrive at her mother's estate in Shio Island (汐島, Shiojima) and meet their relatives Sachio and Sae Sadahama as well as Koichi, a postman and an old friend of Ikuko, who has always had a crush on her. Momo is devastated and misses Tokyo. In the attic, she opens a present containing a rare picture book about goblins and Yōkai, collected by Sachio's father. Three droplets from the sky enter Ikuko's estate and transform into yokai consisting of Kawa, Mame, and Iwa, the group's leader.
When Ikuko begins to take nursing classes, Momo reads the book and begins to hear some strange sounds from the house. She is chased out of the estate by the yokai, only to encounter a young boy named Yota. Oblivious to the house's strange noises, Ikuko and Yota assume that it is safe. The next morning, she meets Yota and his sister Umi. The three meet up with his friends and swim under the bridge, but Momo decides not to and runs to a shelter during a thunderstorm. Iwa, Mame and Kawa soon reveal themselves, having stolen some fruit from around the island. Frightened, Momo runs back to Ikuko's estate and discovers that Sachio's orchard was ransacked. Sachio then tells Momo that the yokai were originally gods, but they were transformed as a punishment for breaking the divine laws.
Momo attempts to prevent the yokai from stealing the local vegetables, only for Kawa to break Ikuko's mirror. Later, she and Ikuko argue and Momo leaves. Shortly after, Ikuko suffers a near-fatal asthma attack while looking for Momo. Upon witnessing Ikuko being close to death, Momo realizes her mistake and asks the yokai to help look for a doctor on the other side of the island. However, the yokai decline and Momo leaves the house. Koichi and Yota pursue Momo, but she reveals her previous argument with Kazuo before his death and asks Koichi to help find the doctor. Meanwhile, the yokai realize that they are able to escape punishment by allowing Momo and Koichi to cross over the newly completed and not yet opened bridge and find the doctor on the other side of the road.
The next morning, Momo writes a letter to her father thanking him as Ikuko recovers. Having completed their mission to protect Momo, Iwa, Mame and Kawa transform back into the droplets and return to the sky. That night, Momo and Ikuko reconcile during the tōrō nagashi and the two eventually realize that Kazuo wrote that he was proud of her. Later, she begins her new life with Yota and the other children by swimming under the bridge.Karen Miyama as Momo Miyaura.
Yuka as Ikuko Miyaura, Momo's mother.
Toshiyuki Nishida as Iwa
Kōichi Yamadera as Kawa
Chō as Mame
Daizaburo Arakawa as Kazuo Miyaura, Momo's father
Yoshisada Sakaguchi as Sachio Sadahama
Ikuko Tani as Sae Sadahama
Takeo Ogawa as Koichi
Kota Fuji as Yota
Katsuki Hashimoto as Umi
Amanda Pace as Momo Miyaura
Stephanie Sheh as Ikuko Miyaura
Fred Tatasciore as Iwa
Dana Snyder as Kawa
Bob Bergen as Mame
Kirk Thornton as Kazuo Miyaura
Frank Ashmore as Sachio Sadahama
Philece Sampler as Sae Sadahama
Rick Zieff as Koichi
Kanoa Goo as Yota
Mia Sinclair Jenness as Umi
Distributor Kadokawa Pictures announced this film in its lineup of 2011 and 2012 films on 15 February 2011. More details of the film were announced on 11 July 2011. It was announced that the director Hiroyuki Okiura will be in charge of this film. His previous work as a director includes the 2000 film Jin-Roh: The Wolf Brigade. The film A Letter to Momo is Hiroyuki's first film in 11 years after Jin-Roh. He had spent 7 years coming up with the script, directing the film and creating the storyboard for this film.
The main voice cast members of A Letter to Momo was first announced on 17 November 2011. It was announced that actress Karen Miyama voiced the 11 year old lead character Momo, while singer Yuka is voicing Momo's mother. In addition, actor Toshiyuki Nishida voices Iwa in the film.
In an announcement made on 11 July 2011, it was revealed that the theme song for the film A Letter to Momo is the song Uruwashimahoroba ~ Utsukushiki Basho ~ (ウルワシマホロバ～美しき場所～) by Japanese singer Yuko Hara. This song is an acoustic piece, and it creates an image of the rich natural scenery of the Seto Inland Sea. The "美しき場所" in the song title is the old way of describing "a beautiful place to live". Hara wrote the song's lyrics and composed the music, with Junichi Soga as the editor of the song.
Yuko Hara, who is the keyboardist for the Japanese band Southern All Stars, reportedly spent 5 years working on this piece of music. She said that "I loved animation from a very young age, so being able to contribute the theme song for this film makes me happy and honored.".
A Letter to Momo made its international debut at the 2011 Toronto International Film Festival that took place from 8 to 18 September 2011. It was screened at the festival under its "Kids" programming. Later, it was announced that the film will be shown at the 44th Sitges International Fantastic Film Festival that ran from 6th to 16 October 2011 and at the 16th Busan International Film Festival, which took place on 6th to 14 October. It will be shown in Busan as part of the festival's "Wide Angle" program.
Additionally, A Letter to Momo was screened at the 27th Warsaw International Film Festival. This is the first Japanese anime film to be showcased at the Warsaw International Film Festival and it competed at the festival under its International Competition section. Also, it was announced that this film will be competing for the Halekulani Golden Orchid Award at the 31st Hawaii International Film Festival, which took place from 6 October to 16 October 2011.
A Letter to Momo made its US continental premiere at the New York International Children's Film Festival that took place March 2 to 25, 2012.
It was featured in the Boston International Children's Film Festival, which ran from August 18 to September 1, 2013 at the Museum of Fine Arts, Boston.
GKIDS distributor New Video/Cinedigm released A Letter to Momo on bilingual DVD and Blu-ray in the U.S. on October 21, 2014.
A Letter to Momo was released in Japanese cinemas on April 21, 2012, debuting in over 300 theater screens on its opening weekend.
The film grossed $4,969,070 in Japan, $1,700,694 in South Korea, $6,409 in Hong Kong, $1,003 in Belgium, and $71,712 in the United States, for a total of $6,748,712 worldwide.
The review aggregator website Rotten Tomatoes reported an 80% approval rating with an average rating of 6.7/10, based on 30 reviews. The website's consensus reads, "Sweet, sad, and visually striking, A Letter to Momo is a hand-drawn experience for animation fans to savor." On Metacritic, the film achieved an average score of 65 out of 100, based on 11 reviews, signifying "generally favorable reviews."
Mark Schilling of The Japan Times said that Okiura "manages [the film's] transition from light to serious with the craft and assurance of a true storyteller, while firmly grounding his human and nonhuman characters in their Seto Inland Sea setting, from the narrow portside streets to the gloriously expansive view from the island’s highest point," and also praised the film's hand-drawn animation. Jeannette Catsoulis of The New York Times also praised the film's look and said, "As Momo conquers her fears, averts a tragedy and finally sees the beauty of her surroundings, the movie grabs your heart with the softest of hands."
A Letter to Momo was adapted into a film manga and will be serialized in the Monthly Asuka magazine, published by Kadokawa Shoten. This manga is written by Akiko Kitami, and the first chapter of the manga was published in the November 2011 issue of the magazine. Kitami's previous works have also previously been serialized in the Monthly Asuka.