Харусаме

Harusame was the former master of Utakata. He was once Utakata's master and he had trusted him until Harusame tried to remove the Six-Tailed Slug from his body which resulted in Utakata transforming into the Six-Tails and killing him. Since then, Utakata has held a great grudge against Harusame and made him think a student and master bond is not something to be counted on. Tsurugi states that Harusame tried to remove the Six-Tails to save Utakata, but Utakata believes otherwise. (source: narutopedia)