13 Sentinels: Aegis Rim: Prologue was released on 14th March 2019, and Atlus announced on the same day that the full game will be released in autumn 2019.
— アトラス公式アカウント (@Atlus_jp) 2019年3月14日
Though previously announced for a 2018 release on the PS4 and PS Vita, Atlus announced in late 2018 that the PS4 release would be delayed, and the Vita version cancelled.
Though details on the gameplay and story had been scarce up till now, Prologue has the early portions of each of the thirteen characters playable, adding up to just under 3 hours of playtime.
13 Sentinels takes place in a world being invaded by gigantic mechanical monsters of unknown origin, and mankind has no way of standing against them except with giant robots called Sentinels, but these are only created far into the future. Multiple characters use time travel, jumping back and forth between time periods, while conspiracy and betrayal threaten to jeopardise these efforts to stop the invaders. The time periods involved are 1944, 1984-1985, 2024-2025, 2064-2065, and 2187-2188, with 1984-1985 serving as the main premise for the game. The Sentinels and invaders also follow the characters to these different time periods, and nanomachines used to rewrite memories are also involved, making for an intricate and epic sci-fi plot filled with twists and suspense.
Gameplay as seen in Prologue has no action-oriented elements at all; The game is entirely story-centric, with the player talking to characters and learning new keywords, which can be thought about or used on other characters, to advance the story. The game’s genre had previously been announced as “adventure”, which in Japan is generally used to refer to text-heavy games commonly referred to as “visual novels” in the west, and share the same early roots as western adventure games but evolved separately to prioritise narratives over puzzle-oriented gameplay elements.
Prologue also includes a teaser trailer for a new project by Vanillaware, unlocked upon clearing all 13 chapters, which appears to take place in a fantasy setting.
Though no further details on this new project have been announced yet, Atlus has stated through an official video featuring Mafia Kajita playing the game that there will be an official announcement once 13 Sentinels is completed.
13 Sentinels: Aegis Rim will released for the Playstation 4 in Japan in autumn 2019. 13 Sentinels: Aegis Rim: Prologue has been released, but is only included with purchases of specific items.