You play as a male adventurer, freshly graduated from the adventuring school, Adventum!
Now you must venture across the home continent of the monster girls, Lucidia, in an attempt to get rich, or get fucked into submission trying. Also defeat the Demon Queen. Maybe.
You can also spend time getting immersed in the games whimsical setting and (usually) upbeat tone as you get to know some of the monster girls.
They might even hold your hand instead of trying to fuck you silly.
Monster Girl Dreams is a RPG that uses a sex and lewd techniques in order to defeat your opponents instead of more conventional forms of battle, all while not trying to give into the enticing pleasures they offer.