Yuki Tachibana, a withdrawn third grader, is convinced that the fourth floor of his school is home to supernatural creatures that few kids (and no adults) can see and he's worried about a recent influx of new, less friendly creatures and about his ability to perceive the true shape of things waning as he gets older. Most of the other kids mock Yuki - they think he's crazy due to his strange pronouncements and peculiar actions - and, aside from the creatures he sees, his only social interactions are with the school's kindly and open-minded caretaker, a new transfer student named Makoto Suzuki who's allocated the desk next to his and an enigmatic boy named IQ who always wears a box over his head.