Adult PC Game: Hypnosis v1.4.1 by Expanding universe Archive

You moved in with your best friend and his family under one condition:
That you don't hook up with your friend's cute little sister Leah who has a crush on you.

The game begins with Leah complaining that her boobs are too small, so to make her feel better you pull out your grandfather's pocket watch and wave it in front of her, telling her that her boobs will grow. This somehow works, and soon all of Leah's friends are asking you to hypnotize them also.