After summoning the King of Heroes, Gilgamesh, for the Sixth Holy Grail War, Vivi has to learn how to create a bond with him correctly before going out to fight. "Sheesh, out of all the servants I can summon, I ended up with the most arrogant one of all." "Out of all the mongrels in the world, you're the most annoying."

"Servant, Lancer. True Name, Karna. Nice to meet you, Master." As one of the competitors in the Holy Grail War, Crystal finds a piece of golden armor at her grandparents' house without knowing that she will summon the Hero of Charity.

Vivi has a demon fox spirit possessing her body after an accident that happened a century ago. She now lives in the abandoned temple where the incident occurred. Douma, the religious leader of the Eternal Paradise cult and upholding the tile as Upper Moon Two, found her one night and took her in. "Wouldn't you be happier if you lived here with me?"

"So, how much?" Vivi is a detective working with her senior, Kato Haru, until Kambe Daisuke, an extremely wealthy man, enters her life.