Stepmother Kiyoka's love for her son is too deep. One day, she finds her son's discarded pants and gets excited by the sight, starting to masturbate. Furthermore, she notices her sleeping son's crotch is erect and, unable to resist, licks it all over.
Kiyoka enters the bath without any reason. Her son's dick is too big, and although she knows it's wrong, Kiyoka, having exceeded her limit of restraint, heads to her son's bedroom. She deliciously takes his penis in her mouth and has her son play with her pussy. Then, she approaches her son, leading to forbidden sex.