Hikari (Hikaru Utada song)

"Hikari" (Japanese: 光; "light") is a song recorded by Japanese–American recording artist Hikaru Utada for their fourth studio and third Japanese language album, Deep River (2002). It was released on March 20, 2002, as the third single from the album in Japan. It was written and composed by Utada, whilst production and arrangement was handled by Utada, Teruzane Utada, and long-time collaborator Miyake Akira. The single, and a remix by Russell McNamara (under the alias PlaniTb), was used as the official Japanese theme song for the 2002 action role-playing video game Kingdom Hearts, and appeared on its original soundtrack. Musically, "Hikari" is a pop folk song with lyrics about mysteries in life and human activities.

Upon its release, the track garnered positive reviews from music critics, who highlighted the track as one of Utada's best singles, and commended their vocal abilities and songwriting. It was also successful in Japan, peaking at number one both on the Oricon Singles Chart and Tokyo Broadcasting System's (TBS) Count Down TV singles chart. It was certified double platinum by the Recording Industry Association of Japan (RIAJ) for physical shipments of half a million units. An accompanying music video was shot by their then-husband, Kazuaki Kiriya; it features Utada washing dishes and drinking water. It was performed on some of their concert tours, including the Utada United and Wild Life tour.

For international versions of Kingdom Hearts, Utada recorded an English language version of the song, entitled "Simple And Clean". Both the original edit and remix version by PlanitB served as international theme songs. It did not appear on Utada's English studio album Exodus (2004), but was released as an A-side 12-inch single with Utada's single "Colors" in 2003, and received positive reviews from most music critics. The original version was included on their 2009 English studio album This Is the One. "Hikari" and "Simple And Clean" were rerecorded in 2024, with the former released for their 2024 greatest hits album, Science Fiction, and the latter used in 2024 for the Kingdom Hearts Steam announcement trailer released on YouTube.