Sōichirō Kuzuki
Sōichirō Kuzuki (葛木 宗一郎, Kuzuki Sōichirō) is a fictional character from the Japanese visual novel and anime series Fate/stay night by TYPE-MOON.
He is a well respected teacher at Shirō Emiya's school. He wears glasses and looks fairly serious. He has difficulty expressing his emotions, mostly because he is unable to trust if his emotions are true.
The voice acting for Kuzuki is done by Kazuhiro Nakata.
Abilities
He mainly uses hand-to-hand combat while Caster supports him in the back. In Unlimited Blade Works, Sōichirō surprised and nearly killed Saber with a fighting technique she had never seen before.
Past
Sōichirō's past is revealed only in Fate/hollow ataraxia.
Before he came to Fuyuki City, Sōichirō had been raised from childhood by an organization that trained young children to become professional assassins. The children were raised away from the rest of society in forests in factories which taught them the skills required of killers and treated them like tools. Knowledge of how to life as a normal human was minimized to ensure their adequecy and efficiency.
Sōichirō found that when he accomplished his missions, he felt emptiness rather than any other emotion. Hoping to find meaning in his life, he left the organization and chose to become a school teacher, which was to serve as a cover for his job as an assassin. He found no meaning and felt he only existed.
When he met Caster, he felt something instead him move. While he had no interest in the coming Holy Grail War or Caster, Sōichirō helped her because she asked for it.
Role
Sōichirō is Caster's master.
According to the anime adaption, Sōichirō is not a mage, but a highly trained assassin. After Caster killed her previous master and summoned the servant Assassin, she chose Sōichirō to be her new master. He has no interest in the Holy Grail war and acts mainly according to the will of Caster. The two seem to have a strong love interest in each other.
He dies after Caster does during the anime and the Unlimited Blade Works scenario. According to hollow/ataraxia, he finally realizes that he regretted his whole life and how he killed others, knowing and understanding that what he was doing was wrong yet still continuing that kind of life. Uncertain of how to repay his debt, he suffered whole life yet managed to find some peace with Caster. In the anime, he tells Caster that he is fine after she sacrifices herself to save him and dying moments after her, lying so that Caster would die happy.