Mahoro Andou, a formidable combat android created by Vesper to defend Earth from extraterrestrial threats, faces a dilemma as her operational lifespan dwindles. With only a month left if she continues battling aliens, she could extend her existence by over a year by avoiding conflict. Meanwhile, Suguru Misato, a high school student grappling with the responsibilities of his parents' vacant home, seeks household assistance. Unexpectedly, Mahoro, disguised as a maid, emerges to his aid during a bus hijacking. Embracing a new role, Mahoro opts to spend her waning days as Suguru's maid, fostering deep connections with him and his friends. As their daily lives intertwine harmoniously, Mahoro conceals her true motives, hinting at a shared past with Suguru shrouded in mystery.