A younger sister dozing off in front of her older brother. - Seeing her defenseless appearance, the older brother gets horny and starts masturbating even though he knows it's his sister. - The naughty pranks on the younger sister who won't wake up gradually escalate. - But my sister finds out and gets turned off. - Even so, the kind sister who can't hate her brother must have been filled with evil spirits, right? - and offered to help with masturbation...!