X-Change (PC Games)

You are Takuya Aihara, an average junior college student with one character flaw: you're a bit of a mental weakling. No matter how hard you try, it seems that all the girls around you are constantly pushing you around: your teasing step-sister Natsumi, the genius president of your chemistry club Mami, but especially Asuka, your beautiful childhood friend.

One fateful day, while cleaning some shelves in the chemistry room, you spill a mysterious chemical on yourself. The next thing you know, you've been transformed into a girl! And so begins this hilarious adult-oriented adventure.