The original Gate Keepers was bright and disposable; this one burns it down and builds something colder on top. Ayane carries the weight of 32 years of meaningless war, fighting out of bitterness instead of hope, and the show never apologizes for that shift in tone. What begins as a simple Invader conflict becomes a story about whether saving humanity matters when humanity itself has already given up.

Thirty-two years after the Invaders were first defeated, A.E.G.I.S has been nearly dismantled. It survives as an underground group with only a few Gate Keepers left to protect humanity. Ayane Isuzu is one of them. She is fed up with society in general, yet she keeps fighting the Invaders out of spite toward her father. Then she learns that Machine General and Devil Count have returned, now joined by a mysterious ghost girl. Ayane and what remains of A.E.G.I.S must stop them and save humanity once more in this six-episode sci-fi action drama OVA.