Though he is initially shown as a normal human, it is later revealed that he once had Shinigami powers, and later he is the only one
Who knows about Ichigo's true powers, and who tells Ichigo how to train for the last battle against Aizen.
But the The Lost Substitute Shinigami arc where
Ichigo fights Ginjo, it's revealed that Ginjo was the first Substitute Shinigami.
So what is Ichigo's father and why does he know what he knows? Also, why he doesn't seem to have any Shinigami powers, while he knows so much about them?