Ikuma Dan (1891–1946) was a prominent Japanese composer and music educator, known for his significant contributions to the development of modern Japanese music. His work primarily spanned the genres of classical and traditional Japanese music, blending Western influences with indigenous styles. Dan is best known for his popular compositions such as "Kōjō no Tsuki" (The Moon Over the Ruined Castle), which remains a staple in Japanese music and is often performed in various arrangements. He also composed songs for children's choirs and contributed to the field of music education, promoting Western music theory and practices in Japan. His impact on music is notable for his role in the modernization of Japanese music during the early 20th century, as he sought to create a uniquely Japanese sound that incorporated Western musical elements. This fusion helped lay the groundwork for future generations of Japanese composers. Dan's legacy endures through his compositions and the influence he had on both the traditional and contemporary music landscape in Japan, making him a key figure in the evolution of Japanese art music.