Because I couldn't find any informations about it. At Japanese Wikipedia, there's no information about Asagutsu too. If I don't sure about the yokai's existence, I can't write about it at the wiki. There's a lot of fake and fiction information at English sites and I have to be careful. But send me link to the reliable site that I can find info about Asagutsu if you can. :) Btw, sorry for my English, I'm still learning.