One snowy night, the protagonist, Kanou Izumi, kicked out of his house under some circumstances, lay dying in front of the train station. Unable to move from hunger, his five senses frozen from the cold, he was about to lose consciousness. His feelings were already past despair; he was void of all emotions.
Then, a girl, Shirahase Yuu, a classmate who often skips school, appears. As if picking up an abandoned kitten, she takes him to her apartment.
"Kanou-kun, you are my meal so I'm going to feed you to fatten you up." She smiles faintly as she voices those words.
"This girl is messed up."
Even while thinking that, Izumi had nowhere else to go, and so stays in her apartment. However, Izumi eventually realizes... Yuu is a descendant of the immortal man-eating mermaids.