Board Thread:General Discussion/@comment-13237238-20131018115404/@comment-26420452-20131019053621

I've previously speculated that Ichibei Hyōsube is the inventor of Kidō (what can be more important than inventing Zanpakutō or making a Shihakushō?). Kidō is a Shinigami-specific skill (so it's impossible Quincies invented it) and it's probable that before Ōetsu Nimaiya's breakthrough, it was their main combat skill.