Inside the Soul Society's Central Underground Great Prison's lowest level, known as "Muken," Kenpachi Zaraki removes his eye patch to fight Retsu Unohana, a.k.a. Yachiru Unohana, "The First Kenpachi." As the battle escalates, the two begin to reminisce about the day they first met and fought in the Rukon District, which ended with Kenpachi learning to enjoy the thrill of battle. However, Unohana alone realizes how the same incident has also affected Kenpachi's powers in a negative way. Meanwhile, in the Royal Palace, Ichigo and Renji head to Hoohden to meet Oh-Etsu Nimaiya, the man who is said to have created the Zanpakuto.