Daisuke's mother is going on a trip, so his mother's best friend Miku is going to take care of him instead. His mother's best friend is just an old lady. Daisuke didn't have high expectations, but a busty beauty appeared before him, far beyond his imagination. Daisuke couldn't wait any longer to start living alone with Miku for a while, so he sneaked into the bathroom to use Miku's underwear as a masturbation aid. But unfortunately, he was found out...