Known for their R&B-influenced pop explorations, Hikaru Utada broke through in 1999 with debut effort First Love, one of the best-selling Japanese albums of all time. Hikaru's early style was based heavily on late '90s R&B as they detailed relaxed takes on new jack swing with skipping drum machines and deep bass lines. The innovative artist even called on legendary producer Darkchild to add his recognisable flourishes to her 2000 single "Time Limit". Over time, Hikaru carved out a softer pop sound, diving heart-first into emotive ballads on the likes of "Prisoner of Love" and "Deep River".