Sekiro, also known as Wolf, or Ookami, is the eponymous protagonist of Sekiro: Shadows Die Twice. He is a Shinobi serving the Divine Heir, Kurou. Bound by honor, he is composed and reticent, but he also has the ruthlessness to complete his mission by any means necessary. After losing his arm to Genichirou Ashina, he is gifted the shinobi prosthetic by the sculptor, which he uses on his journey to save lord Kurou.

(Source: Sekiro: Shadows Die Twice Wiki)