My girlfriend's younger sister, Mayu, actively teases and seduces me! She confuses me with her cute smile and straight Hitomi! She suddenly gives me a blowjob in the hallway, then suddenly comes into the bathroom and gives me a titjob, and finally we have secret sex in the bedroom with my girlfriend sleeping next to me! I know that this kind of relationship won't last forever, but I can't control myself anymore! What will be the outcome of this naughty relationship with my fiance's sister...?