User blog comment:Purple sky4/who invented Kido?/@comment-9444583-20130427133249

Based on the info we have now, Kidou comes from the natural energy all spiritual beings have in them. I doubt somebody had to invent Kidou, look, Hachi and Urahara created many new spells of thier own. Rukia could manipulate her energy when she was a little kid, as a mere Plus. I think someone had to standarize and categorize the spells (Kidou Corps with its first Chief, perphas), but would it be an achievement worth getting a promotion to RG? I don't think so.