Fate/stay night chronicles a two-week period in the life of Emiya Shirou, an amateur mechanic who attends school called Homurahara Gakuen in Fuyuki City. Ten years ago, Shirou was caught in a massive fire that incinerated his parents and consumed a large portion of the city; as he was dying, an enigmatic man discovers and treats him. This man, Emiya Kiritsugu, decides to adopt him, though the two maintain a distant relationship because of Kiritsugu’s frequent departures from Fuyuki City. One moonlit night, Kiritsugu and Shirou have a discussion outside of their home, and Shirou discovers a fact about his father that Kiritsugu was actually a mage.
Through their conversation, Shirou learns of his foster father’s failed life ambition to become a “Hero of Justice” (?????, Seigi no Mikata?), a guardian of mankind who could protect the weak and innocent. Touched by Kiritsugu’s conviction, Shirou affirms to his foster father that he intends to devote his life to achieving that distant ideal, much to Kiritsugu’s chagrin. To do this, Shirou pleads with a begrudging Kiritsugu to teach him magecraft (??, Majutsu?); but Shirou proves to be talentless in almost all the fundamental magecraft disciplines.
Kiritsugu warns his son that the life of a magus is one that leads to destruction, but if he is truly set on benefiting people, he should apply his knowledge in secret and hone his craft in private. After Kiritsugu dies, Shirou becomes frustrated with his progress, for he feels inadequate about his good deeds through magecraft and is unsure of how to orient his future to contribute more.
Unknown to Shiro, Fuyuki City is the setting for a secret and violent war among competing magi. For the past two centuries, seven magi were gathered and engage in a Battle Royale, each gambling his or her own life to obtain the Holy Grail, a legendary chalice capable of granting wishes. The past four Holy Grail Wars have typically occurred every sixty years, with the most recent concluding a decade ago, but the fifth war has eerily started prematurely.
Each magus, better known as Masters, are aided by one of the seven summoned spiritual familiars known as Servants, who are the reincarnations of legendary souls from all across time. These resurrected Heroic Spirits (??, Eirei?), possess superhuman characteristics and wield powerful artifacts or abilities called Noble Phantasms (??, Hogu?). A Noble Phantasm’s hidden abilities may be released by invoking its true name, but casual brandishing of a Noble Phantasm is best avoided, for symbolic Noble Phantasms usually belie a Servant’s identity, diminishing that Servant’s competitive advantage. Specific legends may be summoned with the aid of catalysts, which are artifacts, ideas, or experiences similar or of value to the desired Servant. Only one Servant can be summoned in each war from one of seven classes: Saber, Archer, Lancer, Berserker, Rider, Assassin, and Caster.
The Holy Grail is a spiritual artifact, so only astral entities, such as Servants, are capable of touching it; this restriction forces Master and Servant to cooperate with each other against rival pairs, even if a situation entails fighting to the death. Masters control Servants with three Command Mantra (??, Reiju?), which are crystallized miracles issued by the Holy Grail that manifest on a Master’s hand. When activated, Command Mantra permit a Servant to accomplish an incredible feat, or alternatively provide Masters with the authority to issue an irrevocable and absolute order to a Servant. In the event of a Master’s demise, a Servant may choose to bind him or herself to another Master; if a Servant is slain, a Master may ally with a wayward Servant or pursue sanctuary with the Holy Grail War’s impartial supervisor, who is traditionally a delegate of the Church.
After cleaning his school’s kyudo (archery) dojo late one night, Shirou stumbles upon two Servants, Archer and Lancer, battling in the school courtyard. To avoid compromising the war’s secrecy, Lancer hunts down and pierces Shirou in the heart with a spear. For an unknown reason, Shirou’s classmate, Tohsaka Rin, uses an heirloom filled with concentrated prana, Prana (??, Maryoku?), to resuscitate him. Shaken and dazed, Shirou goes back to his home, but is again attacked by Lancer. Shirou weakly defends himself against Lancer but is soon overwhelmed by the powerful Servant’s attack. After the battle prelonged, Shirou falls into his storage room. Cornered, he prepares for the worst; but before Lancer can inflict another fatal blow, a young woman outfitted in armor blocks Lancer’s spear. She drives Lancer away, introduces herself to Shirou as Saber, and greets him with the words: I ask of you, are you my Master?