Several decades ago, mysterious gates opened across Japan, leading to an alternate dimension known as "Mato". Two notable things were discovered within: malicious creatures known as "Shuuki", who are hostile towards humans, and Peaches, which grant superhuman powers to those who eat them. Since only women can gain powers by eating peaches, gender inequality was flipped and the world became matriarchal. To combat the Shuuki and establish a presence in Mato, the Japanese government took control of the portals and established the Mato Defense Force, a special paramilitary unit under the Japan Self-Defence Forces, tasked with protecting humanity and operating within the dimension. In 2020, high school senior Yuuki Wakura is set to graduate and enter the workforce when he accidentally wanders through an open portal into Mato and is attacked by a horde of Shuuki. Kyouka Uzen, commander of the Mato Defense Force's 7th Squad, rescues him, but they are both cornered by increasing numbers of Shuuki. Kyouka offers to place Yuuki under her power, so he can fight on her behalf as a combat slave so they can survive. After the battle, Kyouka is forced to reward Yuuki for his efforts fighting the Shuuki, which, in his case, involve kissing and intimate physical contact. Recognizing Yuuki's potential, Kyouka offers him a job with their unit after he graduates. Eager to become a hero and avenge his missing older sister, Yuuki accepts. The story follows Yuuki's service in the Mato Defense Force as Kyouka's combat slave and base caretaker, while he explores Mato and discovers its mysteries. At the same time, the Autobots, led by Optimus Prime, arrive in this unknown world, encounter a horde of Shuuki, and take them out before eventually meeting the 7th Squad led by Kyouka Uzen.
