Ryota Iijima presents himself as a friendly and supportive guidance counselor at the protagonists' school, encouraging students' ambitions. His appearance reinforces this image, featuring bright, colorful clothing—often a sweater vest—glasses, and a hair clip holding his bangs.

Beneath this approachable facade, he acts as the vessel for the dream demon Mistilteinn (or Mystleteinn). In this role, he systematically manipulates students to become unwilling hosts for other dream demons. Once possessed, Mistilteinn targets these students for elimination, stripping them of their goals and ambitions and inducing a catatonic state known as Dream Loss Syndrome.

His methods involve coercing dream demons into human hosts before Mistilteinn kills them. Ijima displays overt sadism, particularly toward possessed students. For example, after Mistilteinn defeated a dream demon within a female student, Ijima repeatedly kicked her unconscious body, with visual cues implying potential fatal injury from head trauma. He acts without remorse or loyalty, solely to advance Mistilteinn's goal of eradicating human aspirations.

Ijima exhibits parallels to other antagonists in demeanor, including an exaggerated evil laugh reminiscent of figures like Yuuki Terumi. His manipulative tactics include delivering inspirational speeches that mask his true agenda.

His background, origins, and development remain undefined beyond these events. The character does not appear in spin-offs, movies, OVAs, or other extended media.