This paper examines the development process and successful factors of the ringing tone melody downloading service, or “Chaku-Mero,” in Japan. Chaku-Mero, arguably the most successful mobile (m)-commerce business in the world, is a mobile Internet service in which a subscriber could download from a wide selection of music melodies his/her favorite for a fee to get it ring when the mobile phone receives a call or message. This chapter describes the process of how this business has evolved from pre-mobile-Internet phase of related business; examines the structure of the business; and analyzes why some content providers have been more successful than others. Some implications for the prospects of mobile Internet businesses for music and other cultural contents will be provided.