Mahoro Andou is a powerful combat android designed by Vesper, a secret organization protecting the world against alien invaders. Unfortunately, her remaining operational time is running short. If she continues to fight, she will shut down in about one month. However, if she chooses to avoid combat, she can live freely for over a year. Suguru Misato is a high school boy who lives alone in a large house left behind by his late parents. Like any other boy his age, he has trouble taking care of the house on his own, so he decides to enlist the help of a maid. His problem is solved in the most unexpected way: when a couple of thugs hijack the bus he is riding, a young, beautiful girl wearing a maid outfit saves the day. It turns out that this girl is Mahoro, who has chosen to live her remaining days as Suguru's new maid. Mahoro makes the best of her remaining time and develops bonds with Suguru and his friends during their peaceful yet lively everyday interactions. However, Mahoro is hiding her true intentions behind becoming Suguru's maid, and it seems that their pasts are more intertwined than Suguru realizes.

As the relationship between Mahoro, Suguru and his classmates develops further, another android girl enters their lives and becomes attached to Mahoro. All the while, the number of days before Mahoro is to shut down decreases steadily. (Source: ANN)

Three years ago, a bloodthirsty race of interdimensional beings known as the Disas appeared and destroyed everything they could reach on Earth. With regular weapons rendered useless, humanity's only hope of survival relied on humans who became magical girls after forming an alliance with the Spirit Realm, who had followed the Disas to Earth. After a violent conflict, the squad of magical girls emerge victorious, with the survivors now known as the Magical Five. Following the war with the Disas, the Magical Five disbands. Kurumi Mugen, Mia Cyrus, Tamara Volkova, and Lau Peipei independently continue their own military services, while their leader, Asuka Ootorii, retires and becomes a high school student. However, Asuka's peace is short-lived, as it seems there were survivors on the enemy's side as well. As magic must be fought with magic, Asuka is dragged back into combat as an even worse battle looms on the horizon.

In the year 1923, a vampire crisis takes Tokyo by storm. Provoked by the illegal trade of Ascra, an artificial blood source, the population of vampires begins to rapidly increase within the city. Under orders from Lieutenant General Sounosuke Nakajima, the Special Forces Unit 16 gathers vampires within the military to create a new undercover vampire-hunting unit known as Code Zero. Leading the unit is Colonel Yoshinobu Maeda. Responsible for locating the source of the Ascra trade as well as capturing and killing vampires, he is pressured into producing fruitful results amidst the growing criticism that threatens to decommission the unit. To make matters worse, the vampires within the unit are struggling to grasp their newfound powers and identities now that they are no longer human. With the world at odds against them, the members of Code Zero must find a way to curb the crisis or otherwise fall victim to their own demonic natures.