Root Letter: Last Answer

The game plays as an adventure visual novel. In the game, the player must figure out what happened to the character of Aya, a girl who mysteriously vanished after receiving a particular letter. The gameplay is split into two distinct parts: the adventure part, where the player interrogates characters who knew Aya in order to find more information about her, and the simulation parts, where the player reads through past letters from Aya and selects - out-of-universe - their contents, thereby influencing the later portions of the game.

Root Letter is set in Matsue, Shimane Prefecture, where the protagonist arrives in search of Fumino Aya, a pen pal friend from high school who had disappeared for 15 years. After he finds a letter dedicated to him from her that was never sent, he sets out to interrogate her classmates as he wonders if everything Aya had told him had been a lie. The game contains multiple endings based on the player's choices throughout the game.

The game was announced in November 2015, for both the Japanese and international market. It was introduced as the first title in a line of adventure video games by Kadokawa Games, the Kadokawa Game Mystery series. Each entry in the series is planned to contain the same "fictional actresses" playing different roles across different titles. Key staff from Konami's LovePlus series of dating sim games contributed to the game, including character designer Mino Taro, and producer Akari Uchida.

Root Letter was released for the PlayStation 4 and the PlayStation Vita by Kadokawa Games on 16 June 2016 in Japan, and by PQube on 28 October 2016 in Europe and 1 November 2016 in North America. It was also released for Microsoft Windows in Japan on 31 March 2017 and internationally on 7 July 2017, and for Android and iOS in Japan on 25 August 2017.

Root Letter received "generally favorable" reviews for PlayStation Vita, and "mixed or average" reviews for PlayStation 4, according to the review aggregator Metacritic.

During its opening week in Japan, 8,907 copies were sold, of which 4,855 were of the PlayStation Vita version, and 4,052 of the PlayStation 4 version. The two versions were, respectively, the eleventh and fourteenth best selling games of that week in Japan. Despite the game not appearing on the weekly Media Create charts again in Japan, worldwide sales passed 200,000 copies sold by January 2017, making it a commercial success. By July 2017, another 100,000 copies had been sold, bringing total worldwide sales to 300,000, and by February 2018 it had passed 400,000 copies sold. As of April 2022, the total number of series shipments and digital sales had surpassed 500,000 units.

A sequel, Root Film, was released in Japan in 2020, and in North America in March 2021. The game is not a direct sequel, but a thematic one.

An American feature film adaptation of the game was announced in November 2018 by Los Angeles-based film production company Akatsuki Entertainment. The film, produced and financed by Akatsuki Entertainment, is directed by Sonja O'Hara, written by David Ebeltoft, produced by Annmarie Sairrino, Moeko Suzuki, and Kat McPhee, and starring Danny Ramirez, Keana Marie, and Lydia Hearst, began shooting in Shreveport, Louisiana on September 16, 2019. In June 2021, the film's rights were transferred from Akatsuki Inc. to producer Annmarie Sairrino's AMMO Entertainment and Moeko Suzuki's Ammo Inc.