Brook

Sojiro Kusaka

草冠 宗次郎
Sojiro Kusaka was an old friend and rival of Toshiro Hitsugaya when they were younger in the Shinigami academy. Sojiro believes that he's the rightful master of Hyorinmaru, however, he's soundly defeated by a weakened Hitsugaya numerous times throughout The Diamond Dust Rebellion.