[3][4] Set in the universe of the Front Mission series of videogames, the story follows several individuals trying to survive amidst a surprise invasion of their country, while both helping civilians to safety and attempting to stop destruction and damage wrought by Wanzers, a form of combat mecha.

Developers conceived character ideas before the game's planning began, and many changes to their appearances and ages occurred as the story solidified.

[9] The story takes place in the Front Mission series during a conflict between two Eastern European countries, Ruthenia and Garmoniya, formerly Ukraine.

After enemy forces kill Mikhail's unit, he meets Patrick Lemaire, an agent of the Unified Continental States (UCS), posing as a journalist.

Mikhail then recruits him into investigating a conspiracy involving an advanced prototype Wanzer and a virus known as MODS, both of which were secretly being developed in Ruthenia by rogue officials.

As the invasion begins, Olga encounters a young orphan named Julia, whom she pursues to save her from a human trafficking ring run by the Garmoniyan military.

Leonid is framed for the assassination of Novo Slava's liberator and national hero, Ruslan Izmailov, and forced to escape during the invasion.

After a final confrontation, Leonid destroys Ruslan, and the three protagonists are picked up by Patrick's rescue helicopter as an international peacekeeping force arrives to take control of Novo Slava.

If all thirty civilians and four major supporting characters the protagonists encounter through the game survive, a secret ending will play.

It shows Ruslan revealing to Leonid during their final confrontation that Semargl possesses a computer system called M3, which can predict the future.

An after-credits scene shows Koshka uploading all data acquired from the invasion of Novo Slava to M3 before "proceeding with the next phase".

[17] Nabeshima initially thought that the game would revolve around mech robots fighting each other due to the title's Front Mission roots.

[19] Orchestrator Jordan Seigel and audio engineer Shinnosuke Miyazawa also helped record the soundtrack at Abbey Road Studios in London.

[26] On the day the game was released worldwide, Square Enix launched a free downloadable content pack for Left Alive.

[29][30] In Japan, approximately 17,622 physical units for PlayStation 4 were sold during its launch week, becoming the number five selling game of any format.

[6] Jason Faulkner of Game Revolution praised the setting and plot but noted a wildly changing enemy intelligence that would either never miss or ignore the player completely.

[9] James Swinbanks of GameSpot praised the opening and some of the character dialogue but explained that the lack of story set up initially leads to significant plot revelations having no emotional impact.