Only they were Shinigami with dual Zanpakutou for the entire history of the Soul Society until Ichigo Kurosaki obtained his true Zangetsu. Shunsui and Juushirou represent the best of the Gotei 13 ...

he unlocked his true Bankai, the powerful Söö Zabimaru. Ichigo is the best case of this system. He lived for years rejecting Zangetsu, limiting his own power. Once he accepted him ...