Also known asDecayed Killer
	AffiliationHomurahara Academy, Social studies teacher
	ServantCaster
	GenderMale
	BirthdayUnknown
	Height180cm
	Weight70kg
	Place of originUnknown

Background

Before he came to Fuyuki City, Souichirou had been raised from childhood by an organization that trained young children to become professional assassins. The children were raised while isolated from the rest of society in places like forests. They were taught skills required for killers and were treated as if they were tools. Teaching knowledge on living as normal humans was minimal to ensure the skills of the potential assassins in their care would remain adequate and efficient.

He left the organization and appeared in Fuyuki City, two years before the Fifth Holy Grail War. He chose to become a school teacher, which was to serve as a cover for his job as an assassin. He primarily lectures on World History, though he also holds classes in Ethics. Kuzuki is well respected among staff and students. He was well-liked by the chief priest at the Ryuudou Temple and was granted residency in the temple.

Personality

Souichirou is widely regarded as a strict, austere and impersonal man. He is serious, sometimes emotionless and does whatever Caster says in battle even though he does not care about the Holy Grail. He often displays a blank expression. Souichirou found that when he accomplished his first and only mission, he felt only emptiness rather than any other emotion. Hoping to find meaning in his life, he left the organization and became a school teacher. He found no meaning and found that he could acknowledge only his own existence. He described himself as a "decayed killer".

When he met Caster, he felt something move within him. While he had no interest in the coming Holy Grail War, Souichirou helped her just because she asked for it. His motive to fight is similar to Shirou Emiya.

Abilities

Kuzuki is the Master of Caster, but he is not a magus nor does he have Magic Circuits or Command Spells. He only acts as her anchor to the world, while she must subside off of the magical energy taken from the leylines and the town in order to upkeep her existence. His sperm was still capable of stabilizing her enough to establish their contract after she was brought within Ryuudou Temple’s Barrier. Due to his martial prowess and Caster's reinforcement, he is a rare Master capable of only fighting opponents directly rather than acting from a support role.

Kuzuki is a master martial artist whose strength is above that of regular humans, able to deliver blows to a man's temple with enough force to crush their skull. In his pursuit of mastering his martial art in his daily training, he has come upon the ideal form of breathing and walking techniques for a human that not even the talented Saber could attain through training. While not in the realm of those who naturally possess the ability to replicate potent thaumaturgy, his training has "affected him in the perfect way", bringing about a natural and controlled way of breathing and steps that produce no wasted movement. Saber admires and praises him as the greatest she has seen in that one respect.

Kuzuki uses a fighting style called Snake that was the basis for his means of assassination, keeping him without a weapon so as to allow him an easier chance at getting close to his target. He is an extremely fast learner, having mastered the art years before he was set to fulfill his "function", all while still keeping up his daily routine to perfect it over twenty years. Despite such aptitude, he was not taught any new techniques due to only being "created" to be a "snake tool." It is a fighting style that aims at vital weak points like the forehead, throat, heart and spine, each strike launched with extreme precision and quick speed to the point where he can deliver three fatal strikes in a single breath. He has a policy of always attempting to deliver deathblows to the opponent, so those like Shades that can move even without heed of things like destroyed heads or spines require him to change his tactics to disabling their limbs.

Role

Souichirou is not a mage, but a highly trained assassin. After Caster killed her previous master and summoned the servant Assassin, she chose Souichirou to be her new master. He has no interest in the Holy Grail war and acts mainly according to the will of Caster. It seemed that the two have a strong love interest in each other. It's implied that he sleeps with her on at least one occasion to restore her mana, as Shirou Emiya had done with Saber.

Gallery

Fate/tiger Colosseum Kuzuki ending

Fate/tiger Colosseum Caster ending

Kuzuki and Assassin against the shadows

Kuzuki in Fate/tiger colosseum

Fate/unlimited codes opening