Vesper, an undercover organization dedicated to protecting the world from extraterrestrial threats, created a powerful military android named Mahoro Andou. Unfortunately, Mahoro's operational life span is quickly coming to an end. If she continues to engage in combat, she will be deactivated within a month, but if she avoids fighting, she can survive for over a year. Meanwhile, Suguru Misato struggles to manage his large inherited home as a typical teenager. In search of a solution, he hires a lady in a maid outfit to assist him. However, when criminals hijack the bus he's on, the mysterious maid comes to his rescue in an unexpected way. Unbeknownst to Suguru, this maid is actually Mahoro, who has chosen to spend her last days as a domestic helper for Suguru. Mahoro cherishes her limited time, enjoying peaceful yet lively interactions with Suguru and his friends. However, she keeps her true intentions for serving as Suguru's maid hidden, and their pasts may be more intertwined than Suguru realizes.