Hikaru Utada , also known mononymously as Utada, is a Japanese-American singer, songwriter, and record producer. They are considered to be one of the most influential and best-selling musical artists in Japan. They are perhaps best known by international audiences for writing and performing four theme-songs to Square Enix and Disney's Kingdom Hearts video game series: "Simple and Clean", "Sanctuary", "Don't Think Twice", and "Face My Fears".