The Holy Grail is a legendary treasure in the stories that can fulfill any wish of its possessor. The ritual conducted to obtain the Holy Grail is known as the Holy Grail War. Those who participate in the Holy Grail War are magicians chosen by the Holy Grail, called Masters (in English) or "Shujin" (in Japanese). The heroes bound to them, called Servants (in English) or "Sousha" (in Japanese), are their magical familiars with whom they form a contract. These Servants are seven heroic spirits chosen by the Holy Grail and classified into seven classes, summoned as familiars. Only one group can ultimately obtain the Holy Grail, and this group eliminates others to be the last standing.
The protagonist, Emiya Shirou, a magician who basically has no talent for magic, accidentally forms a contract with one of the Servants, a swordsman, and gets entangled in the Holy Grail War. During the events, Shirou discovers that he has fallen in love with the Servant he summoned. However, he eventually learns the truth about the Holy Grail and ends up destroying it himself, causing him to lose it all.