Morgan's life is going nowhere and he hates it. He's stuck at a low paying job after he dropped out of college. He survives by eating only cheap food in a tiny apartment.
When a ship that he's on to visit his parents sinks, he's unable to get to the lifeboats in time. Just before he runs out of air, he sees a light and finds himself in a strange world ruled by monster girls. In this world he encounters three of them, one after the other.
Each of them want him to be their husband because there are only females of their species, so monster girls only have humans to choose from if they desire children. Due to how their world works, there is a very short time limit on Morgan's choice. The three girls decide to have one day with him each and one shared day with all of them. Afterwards, he will decide who he likes best.