Keita Amano is a perfectly mediocre loner with no particular distinguishing features other than his love for games. One day, his school's prettiest girl and Gamer Club President Karen Tendo suddenly calls out to him. That moment changes Keita's life forever, as he now finds himself in the midst of a romcom with beautiful girl gamers... or, well, that's how it usually goes. Not with him, however.
The Alzano Imperial Magic Academy is located in the southern part of the Alzano Empire and is among most prominent magic schools in the world, where students can learn the highest forms of magic. All those who strive to learn magic dream of studying at this academy, and its students as well as its teachers are proud to be a part of its 400-year history. Glenn Radars is a new instructor who has suddenly been appointed to teach part-time at this highly respected academy. The previously unheard-of lessons of this man known as a good-for-nothing bastard are about to begin.
Four years ago, Kazuma Kannagi was defeated by his cousin Ayano Kannagi for the right to be the successor of Enraiha, a sword passed down in the Kannagi family. His defeat, along with his lack of talent for En-Jutsu, the fire arts, the Kannagis' specialty, resulted in his banishment from the family. Now, Kazuma returns as Kazuma Yagami, a skilled master of Fū-Jutsu, the wind arts.
Year 526 of the Liturgical Calendar. The world knew that witches existed, and that they practiced the notorious art of sorcery. Nevertheless, the world did not know anything about the study of magic. Our story follows a half-man, half-beast mercenary; humans mockingly call his kind the “fallen beasts”. He always dreamt of becoming a human, but one day, he met a witch who would change his life forever. “Do you desire a human form? Then be my escort, mercenary!” The witch introduced herself as “Zero”, and explained that she was searching for a one-of-a-kind magical tome that bandits had stolen from her lair. Entitled “The Book of Zero”, the grimoire supposedly contained valuable magical knowledge that could be used to effortlessly bring the world to its knees. Thus, in order to realize his dream of becoming a human, the mercenary must accompany Zero on her journey—despite her being one of the witches he so loathed. This is the story of a haughty sorceress and a kindhearted beast.
Sixteen years after the "Law for Public Order and Morals in Healthy Child-Raising" banned coarse language in the country, Tanukichi Okuma enrolls in the country's leading elite public morals school and is soon invited into the Anti-Societal Organization (SOX) by its founder, Ayame Kajou. As a member blackmailed into joining by Ayame, Tanukichi ends up taking part in obscene acts of terrorism against the talented student council president Anna (for whom Tanukichi has a crush on).
Invertia was a meteor storm that caused an unprecedented disaster during the 20th century. Because of this disaster, numerous cities around the world were destroyed. However, within the meteor, an unknown element called mana was discovered. It allowed human technology to make rapid strides giving rise to a new species of super-powered humans, the Star Pulse Generation (Genestella). The Festas (Star Warrior Festivals) host battles between Genestella at a city of six academies called “Rikka,” also commonly known as “Asterisk.” Scholarship student Ayato Amagiri transferred into Seidoukan Academy in order to fulfill his own wish, swearing he too will fight in this city.
After a traffic accident, Kazuma Sato’s disappointingly brief life was supposed to be over, but he wakes up to see a beautiful girl before him. She claims to be a goddess, Aqua, and asks if he would like to go to another world and bring only one thing with him. Kazuma decides to bring the goddess herself, and they are transported to a fantasy world filled with adventure, ruled by a demon king. Now Kazuma only wants to live in peace, but Aqua wants to solve many of this world’s problems, and the demon king will only turn a blind eye for so long…
The setting is a parallel world to Fate/stay night where the Greater Grail mysteriously disappeared from Fuyuki after the Third Holy Grail War. After many years of silence, around the same time as the Fifth Holy Grail War would have happened, the Yggdmillennia, a family of magi, openly declares their secession from the Mage's Association, and that they are in possession of the Grail. The Association dispatches fifty magi to retrieve it, and all but one are instantly slaughtered by a mysterious Servant. The one remaining manages to activate the reserve system of the Greater Grail, allowing for the summoning of fourteen Servants in total. In the city of Trifas, two factions will fight for the control of the sacred relic, each of them possessing their own team of seven Servants: the Black Faction whose members are part of Yggdmillennia, protecting the Grail, and the Red Faction whose members were sent by the Mage's Association, trying to take the Grail back. For an event of this scale, the Grail itself summons its own Servant, the holy Ruler, to oversee the conflict. This marks the start of the Great Holy Grail War.