High school student Yumeji Fujiwara has the ability to see people's dreams. Despite the visions never appearing clear or concrete, he is able to predict them by sensing the person's "aura." Normally, this skill is a fun trick to play on his classmates, but Yumeji only ever sees himself having the same nightmare every night. To his surprise, the nightmare continues in the middle of the day even before Yumeji has fallen asleep. The unexpected event was triggered by a dream demon—an inhabitant of the world of dreams who wants to use Yumeji's body as a vessel to fully enter the real world. However, Yumeji is saved by the timely arrival of Merry Nightmare, another dream demon who can somehow physically manifest without a host and is instead trying to return to her own realm. As more dream demons continue to push into reality, it is up to Yumeji and Merry to fight back against the invasion before everyone's nightmares materialize. Yumekui Merry begins with Yumeji Fujiwara, a seemingly average high school student. But ten years ago, Yumeji gained the ability to see the dream auras of other people around him. This ability allows Yumeji to predict what type of dreams people are likely to have next. The dreams of others may not be a mystery to Yumeji, but his own dreams have recently left him puzzled. In dream after dream, Yumeji has been pursued by an army of cats lead by John Doe, who claims he needs Yumeji's body to enter the real world.