A new Holy Grail War is emerging in Snowfield, Nevada, where mages from around the world summon Servants, heroic spirits drawn from myth and history, to fight on their behalf. However, this war seems to differ from previous ones. The organization behind it appears to have used data from the Fuyuki Grail War for their ritual, resulting in strange happenings. Unbeknownst to most participants, this budding conflict is actually a fake Grail War. There exists another set of seven true Servants who are summoned to fight in the genuine Holy Grail War. One of these Servants is a powerful Saber-class who saves the life of Ayaka Sajou, his apparent master, after being summoned. With hidden agendas and unpredictable forces at play, the line between the fake and true Grail War becomes unclear, turning Snowfield into a dangerous battlefield.

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.

Set in an Eastern fantasy setting, Dān Fěi and her brother, guardians of a sword known as the Tiān Xíng Jiàn, are pursued by the evil Xuán Guǐ Zōng clan, who seek to obtain the sword for their master, Miè Tiān Hái. While her brother is defeated, Fěi, who possesses the sword's crossguard, escapes and finds herself in the care of the wandering swordsman, Shāng Bù Huàn, and a mysterious man named Lǐn Xuě Yā, who become her protectors from the pursuing Xuán Guǐ Zōng clan.