Rika Kakiuchi (垣内りか, Kakiuchi Rika, born 31 July 1980), professionally known by her stage name, Rina Aiuchi (愛内 里菜) and formerly known as R, is a Japanese singer, songwriter, businesswoman, fashion model, and YouTuber. Born in Higashiōsaka, Japan, she won the first season of the audition Super Starlight Contest, winning a recording contract with Giza Studio. Her eurobeat-sounding debut album, Be Happy (2001) was certified gold in Japan and spawned a top-five single, "Koi wa Thrill, Shock, Suspense", which served as the theme song to the Japanese anime television series Case Closed. Aiuchi's second album Power of Words became her best-selling album, selling over 419,000 copies nationwide and certificated platinum in Japan.
In 2010, Kakiuchi announced her retirement from the music industry and founded a dog clothing brand Bon Bon Copine in September 2012. She later resumed her musical activities, appearing on several television shows in 2015 and releasing a single "Warm Prayer" in 2018 under the new stage name, R.