Rentarou Aijou has it all: looks, intelligence, athletic skill, and popularity with peers and mentors alike. Unfortunately, none of these qualities help Rentarou with his love life. On the day of his middle school graduation, he is once again turned down by a girl he confesses to, earning his one-hundredth rejection in a row. Down on his luck, he goes to a matchmaking shrine and wishes to finally get a girlfriend in high school. When the god of the shrine suddenly appears before him, Rentarou is told he will meet an astronomical total of one hundred soulmates in high school. Though Rentarou initially does not take this foretelling seriously, his doubts disappear when, on the first day of school, he meets two of these soulmates—Hakari Hanazono and Karane Inda—who both confess to him. With fated encounters and love confessions galore, Rentarou's life is about to get a lot more exciting.

centers around an imperfect copy of a Grail War based on the Third Holy Grail War in Fuyuki. Following the conclusion of the third Grail War, a US-based organization with magi distinct from the London-based Mage Association, used data from Fuyuki's Grail War to plan their own ritual. Seventy years later, they used the city of Snowfield as the Sacred Land for their own Grail War. However, they were unable to successfully replicate every aspect of the ritual, resulting in it acting only as an imitation that has lost the Saber class and allowed for the summoning of strange Servants due to the blurring of the definition of a "hero." Rohngall and his pupil, Faldeus, have been dispatched by the Mage's Association to investigate the city and the state of the war. Faldeus, a US organization spy, has Rohngall sniped upon his arrival, despite knowing that Rohngall is a puppet. He declares that their Holy Grail War has been in development and is real, causing a commotion at the Clock Tower, and that he wishes to "advertise" the project to the Association.