This review discusses the concept of the Art Brut and its origin, as proposed by Dubuffet, along with its unique development in Japan. In Japan, Art Brut has evolved in distinctive ways, particularly in psychiatry. Notably, Art Brut is not synonymous with art created by individuals with mental disorders. Instead, it refers to raw, creative art uninfluenced by existing cultural norms and conventions. Art Brut works often have a psychiatric background, but this is not a defining feature. This review highlights the work of Yuzo Saeki, a prominent Japanese artist associated with Art Brut, and draws comparisons with Jean Fautrier. Finally, this review examines the creativity and originality of individuals with mental illnesses, particularly schizophrenia, from a neuroscientific perspective. It explores genetic factors, brain function alterations, and the interaction between mental illness and creativity in the context of Art Brut. Art Brut offers a deeply moving artistic experience from a psychiatric perspective, and art therapy may play a significant role in the treatment and welfare of individuals with mental disorders. Significant aspects of this field remain unexplored, and further research and development are highly anticipated.