Kiritsugu Emiya is a key character in the Fate/stay night series, known for his complex and morally ambiguous nature. He is a skilled magus and a master of the Einzbern family during the Fourth Holy Grail War. Kiritsugu is driven by his desire for world peace, often using ruthless and pragmatic methods to achieve his goals. He is the adoptive father of Shirou Emiya, the protagonist of Fate/stay night, and his past actions significantly impact the events and characters within the series. His character explores themes of sacrifice, idealism, and the cost of achieving one's ideals.