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Our subject is a 55-year-old man and a former civil servant. He claimed to have seen someone who others could not see. He believed that he is an important person. He had strange behavior such as separating himself from others, speaking and laughing alone, and collecting rubbish. Based on the assessment through observation, interviews, and psychological tests, the subject was diagnosed with schizophrenia and behavioral problems such as collect things. The subject’s behavior appears because he feels pleasure after collecting goods. He did not do other activities that make him feel good; thus, the behavior was repeated. The intervention aims to reduce the frequency of collecting things through negative reinforcement and rewards techniques. The intervention eventually suppressed the behavior of collecting things carried out by the subject gradually.