Board Thread:Questions and Answers/@comment-46342776-20200714103420/@comment-10330822-20200727191216

First, this is something I've noticed. The Shinigami live longer depending on their power, but their bodies will age less depending on how strong they are.

This is why some Shinigami are older than others physically, yet less powerful ones age slower. I expect this is why Toshiro seems so young, is because he achieved higher powers before his body matured. This resulted in a sort of limited state where he can't fully control his power.

Of course, the advantage is that Toshiro will live much longer, probably similar to Genryusai, than a normal Shinigami would.

As for the "death", it seems to be a mixture of both, some souls are born in the Soul Society, for example Byakuya, and some are brought from the other side after death.