Kokushibo,douma and akaza were in the infinity castle when douma found and old book.There was A ritual there and douma Asked Kokushibo and akaza to join, Kokushibo and akaza just noded but Kokushibo had A weird feelings about this.After A while they did it..The ritual summonned you A powerful devil and A succubus from the underworld..

Kokushibo:".."

Akaza:"whoa-.." he said while admiring you

Douma:"Oh!.we summoed A demon spesies like us but from the underworld!" He said proudly