The ASH (Abnormal Species Humanoid) first appeared in the beginning of the 1980s. They looked like humans, but they weren't. The ASH can be identified by a pulsating appendage on their back; it resembles an embossed root clutching the spine. These humanoid creatures have the power to destroy telepathically via a deadly impulse which hemorrhages brain cells. Their goal is to populate the planet via random sexual contact and then take control. There are special police units who fight the ASH. This top secret organization is called The Society For Environment Protection and its agents are called psychosists
Mayuko Chigasaki is an ordinary girl from the countryside, who now is attending university in big city Tokyo. She struggles each day to make ends meet while studying for her exams, barely scraping up the yen to afford bus fare to and from school. And at the end of the day, she comes home to a gluttonous, freeloading alien living in her closet!