Write a story, in salacious detail, at maximum length and focusing on dialogue, from the following premise: The two perverse sisters, Satsuki, the elder and reserved; Ryuko, the younger and brash, ruled over the vast Kiryuin empire as equals. They had turned every woman they crossed into their bidding footslave, through their unusual method of punishment— tickling. But the two sisters had begun in secret to harbour a desire for eachother. Not any desire, however: Ryuko dreamt of becoming Satsuki's permanent footslave, fearing her feather and worshipping her soles. But even more bizarrely, Satsuki wanted to be the exact same thing to her sister Ryuko.