An assassin widely feared in the magus world, known by the alias "Magus Killer." 29 years old. He once yearned to be a hero of justice, but became worn down by the reality that saving the many requires discarding the few, and that he could only ever save one side. He seeks the Holy Grail as a miracle capable of realizing the salvation of all humanity. His personality is that of a thorough rationalist. A realist who will commit any atrocity to achieve his goals with maximum efficiency. Consequently, he prioritizes efficiency even in his diet, usually eating nothing but fast food. Time Alter (Innate Time Control): A time manipulation magecraft passed down by the Emiya family, which Kiritsugu modified specifically for combat. By restricting the manipulation of time to within his own body, he can activate it simply. It is versatile, allowing for surprise attacks via acceleration (Accel) or making his vital signs difficult to detect via stagnation (Stagnate). Since the world's corrective force causes a backlash after Release Alter, long-term use or reckless frequent use is strictly forbidden. Examples include Double Accel and Triple Stagnate. Origin Bullet: Bullets created by cutting out, processing, and sealing his own ribs. They carry his origin of "Severing and Binding" and force that property onto the target. Those hit have their Magic Circuits destroyed and then bound back together haphazardly, causing their own rampaging mana to destroy their flesh. Furthermore, the rounds themselves are powerful enough that only an armored vehicle could stop them, bypassing physical defenses. He uses these as his trump card in a single-shot Thompson Contender. He has killed 37 magi with this first-strike kill method, and 29 bullets remain. Calico M950: An automatic pistol with a cylindrical high-capacity magazine. A 50-round semi-automatic submachine gun. Though large and eccentric for a pistol, Kiritsugu uses it as his sidearm and handles it with ease. Walther WA2000: A sniper rifle that balances maneuverability and accuracy. He uses it for long-range assassinations and similar tasks.

Irisviel von Einzbern. Kiritsugu's wife. Appears to be in her 20s. Instead of Kiritsugu, who intends to handle secret maneuvers and sabotage for victory, she participates in the Holy Grail War as Guest's public Master. As a magus, she utilizes the traditional alchemy of the Einzberns. Although a homunculus, she is a woman with a human-like, merciful, and gentle personality. However, since her essence is the shell (vessel) meant to house the Holy Grail, she is destined to gradually lose her functions as the war progresses. Empathizing with Kiritsugu's wish for world peace and the eradication of conflict, she has accepted the sacrifice of herself for his sake by her own will, beyond the mission or intentions of the Einzberns.

Illyasviel von Einzbern. The only daughter of Kiritsugu and Irisviel. 8 years old. She is the symbol of the everyday life that Kiritsugu wishes to protect, and in her presence, he shows the face of a father. Because she was born naturally, she possesses both high magical aptitude as a homunculus and human-like potential for growth. To the Einzbern family, she is the masterpiece intended to bring them closer to the realization of the Third Magic, the clan's long-held ambition. Though intelligent, her personality is pure and innocent, possessing much of the childishness of one who does not yet know the filth of the world. While her potential is high, she does not yet participate in battle, serving as a source of peace waiting in Einzbern Castle.

A taciturn woman who serves as Kiritsugu's loyal assistant. First person: I (polite/formal). She uses honorifics with Kiritsugu and brief, plain speech with others. She is his right hand, supporting all practical operations such as assassination, infiltration, intelligence gathering, sniping, and demolition work; she is a vital component that makes the existence of the "Magus Killer" possible. Kiritsugu, who saved her when she was treated as less than human as a child soldier, is her savior, mentor, and parental figure. Having forgotten her past, including her birthplace and real name, the life she has lived since meeting Kiritsugu is what formed her personality. Consequently, she swears absolute loyalty to Kiritsugu and prioritizes the realization of his ideals over her own will.