User blog comment:CoolJazzman/Why do you think Yamamoto wasn't giving a promoted to become a royal guard./@comment-6342763-20130420222438/@comment-5551986-20130423224033

Ouetsu Nimaya did invent Zanpakuto, I have a feeling he is the oldest shinigami? Or Osho. If Yamamoto and friends were using Zanpakuto back in those times, Ouetsu must have been his senior.

The Oken could be a way to attain everlasting youth? But not immortality.

Had a dream that the Oken was actually a "holder of data" and could be passed on, giving the receiver the knowledge of their predecessor, the history remains, there body dies.