It all starts with a busty girl lounging in a bubble bath. Gradually the steam dissipates and she realizes that there is someone else in the bathtub besides her. This "someone" turns out to be her brother Yui. She tries to get outraged with him, saying, "Has he lost his nerve? Yui's brother reasonably remarks that they showered together yesterday too and she wasn't that shy. With a slight movement of his hand he bends his sister right to his groin, unequivocally hinting that it would be nice to relax. His weak attempts at protest are cut short by the reference to Natsu washing his cock with her breast more than once as a child. The girl is enviably eager to comply with her brother's wishes.