A naughty older sister who shows off her sex with her boyfriend, knowing her younger brother is watching. She comes to where her younger brother is masturbating in the bathroom and starts stroking his erect penis, saying, "You have to peel the foreskin and wash it properly, right?" She teaches his penis with her mouth, saying, "I'll give you a sex education," and makes him use toys in his room, turning on his sexual desire. Mao's masochistic nature is revealed when she gives a deep throat blowjob to her excited brother's erect penis. This time, her older sister is made to cum so much that she convulses with her brother's hard thrusts and screams.