Based on a manga by Mitsunaga Yasunori, serialised in Monthly Shounen Sirius. Hiyorimi Hiro moves to a new city to live with his older sister, but dies before he can find her. He then awakens to a new life as a servant of a Princess of the Monster Realm, who just happens to be employing his sister. Monsters soon appear to attack or pester the princess since she is in line for the royal throne, and Hiro must protect her with his life (and repeated deaths). (Soure: ANN)

The Sablum Empire has been attempting to take over the kingdom of Windland for many years, and are now plotting with the mercenaries Sister Hell and Darkness Knight to start a new offensive using powerful magical beings called Angels. Hyaweh, a carefree yet talented swordsman, and Priecia, who just might be the lost princess of Windland, are enrolled at the Knight's Academy in Windland to hone their skill at swords and sorcery. There they meet many friends and allies who can help them protect their homeland from the impending invasion.

A victim of endless bullying, Aito Eyama is plagued by his classmates' constant taunts and beatings. However, through a fortuitous turn of events, he receives a strange invitations for the Captivity Game, where victory promises unbelievable wealth. To participate, he must accept the role of captor and choose one victim to imprison for a month. For Eyama, the only choice is Aya Kirishima, the ringleader of his bullies and the source of all his suffering. The rules of the game are simple: the jailer may do whatever they please with their inmate barring murder; but in order to win the game, the captor's identity must remain hidden. Exemption from the law, an isolated cell, and the funds to purchase supplies—all the necessary tools are provided. As Eyama administers his sadistic revenge and divine retribution, he encounters other captors, each with their own hidden agendas. Meanwhile, Aya refuses to be a compliant prisoner and will go to any length to escape captivity. However, her endeavors threaten to awaken a darkness buried inside Eyama that craves to be unleashed.