Yumeji Fujiwara, a young male student like any other, gained the power to see the aura of other people's dreams, and the ability to predict what kind of dream they will have next, after an event that occurred 10 years ago. Since then, he started to have strange dreams of cats following him for an unknown reason, where he learns, thanks to the boss of the cat army, John Doe, that his body is needed to access the real world. One day, as he was about to return home after his errands, a mysterious girl falls on top of him. This girl, called Merry Nightmare, is actually a dream demon, who's searching for a way to go back to her world. As Yumeji decides to help her, the gate to the world of dreams opens again, this time in full daylight. She appears in the daydream worlds looking for an answer to how to get back to her world. Meanwhile, an evil dream demon named Pharos Hercules is leading other dream demons to make humans into their vessels in order to raise an army, killing those that oppose him which causes humans to lose sight of their goals and ambitions. Yumeji eventually becomes Merry's partner, using his ability to scout out dream demons so Merry can hunt them.