Amidamaru

Samurai that died during the Muromachi period 600 years ago—now is Yoh's ghost companion. He is very powerful and wise but quite taciturn and extremely devoted to "Lord Yoh" ("Yō-dono" in Japanese). He was greatly known around the town of Funbari, where he had died 600 years prior after killing several hundred other samurai soldiers during a battle. He is the original handler of the legendary sword named "Harusame," meaning "Spring Rain," a sword forged by his best friend, Mosuke, who also appeared in the anime/manga as a spirit. This very same sword was reproduced as a "spirit sword" and used by Asakura Yoh during the Shaman Fight. The original was kept in a museum. His name is based on the Buddha Amitabha, the principal figure in the Pure Land Buddhist sect.

(Source: Wikipedia)