User blog comment:MaatRa91/Isshin a substitute shinigami?!/@comment-1712587-20100624125845

if you think about it being a substitue shinigami isn't so crazy. maybe he wasn't human but a soul who was part time on the G13 records but not many people knew about him. It's just as plausible as saying he used to be a Captain five minutes ago and now no one recognises the Son with his signature ability being his.

as in not really plausible but better than some crazy ideas i've heard!!