13 Sentinels: Aegis Rim (十三機兵防衛圏) is a self proclaimed "dramatic adventure" game released by Vanillaware and Atlus for the PlayStation 4 where the player swaps between the stories of 13 characters who are all trying to defend the Earth from an alien invasion. The game was released in Japan on November 28, 2019 and, a few months earlier in March, a Prologue version of the game was released that contained the first three hours of the game. An English localization was published in the United States courtesy of Atlus USA almost a year later on September 22, 2020.
The title is separated into three sections: Remembrance, Destruction and Analysis. Analysis is simply an archive that allows the player to view key words and other information they have gathered throughout the game. However, the Remembrance section has the player control one of the 13 protagonists as they explore environments, talk to NPCs and collect key words that can be used to advance the story. The narrative is structured non-linearly so the player can swap to different protagonists in different orders to experience the story in a number of ways. Depending on the player's actions, a character's story can also branch with the player being able to re-do scenes to get different outcomes. Certain scenes in Remembrance will also progress in real-time with NPCs acting independently of the player's input. At any point the player can also go to the Destruction section where they will participate in real-time tower defense strategy gameplay where the characters control mechs that fight off alien threats.