S1·E2 The Tomb Of Karma

A corrupt wandering samurai attacks Kuro and Kuromitsu in the town near her home and beheads Kuro. Kuromitsu kills the samurai and attaches Kuro's head to the samurai's body. In flashback, Kuro drinks Kuromitsu's blood, but before his transformation can complete, they are attacked by an enemy who has been hunting Kuromitsu for the secret to her immortality. Kuro is beheaded by Benkei, whom the enemy had recruited to be their new leader.