怪盗Rのテーマ (Phantom Thief R's Theme) is the signature track from Sega's 2012 Nintendo 3DS rhythm adventure game Rhythm Thief R: Emperor Napoleon's Legacy (リズム怪盗R 皇帝ナポレオンの遺産). Composed by Tomoya Ohtani, a longtime Sega sound team member best known for scoring much of the Sonic the Hedgehog series, the piece captures the theatrical espionage atmosphere of its source game with a driving beat, bold brass fanfares, and a swashbuckling melody that evokes rooftop chases and museum heists. The song was present in the very first maimai arcade cabinet release on September 13, 2012, placing it among the oldest tracks in the entire series library. It originally appeared with Standard-style charts only, and over the course of a decade those charts underwent numerous level adjustments as maimai's difficulty curve evolved across versions, from maimai+ through BUDDiES+. More than thirteen years later, during the CiRCLE version in October 2025, the song received a complete set of DX-style charts (Basic through Master) incorporating Touch notes, unlocked via Otomodachi Taikai Season 25 SP rewards. The DX Master chart, designed by Luxizhel at a level constant of 13.2, stands as the most demanding arrangement of the track. Its Standard counterpart, charted by 譜面-100号 at level 12.7, had long served as a mid-tier boss for veteran players accustomed to the original maimai lineup.