"Passion" is a song recorded by Japanese-American singer Hikaru Utada, taken as the fourth single from their studio album Ultra Blue (2006). It premiered on December 14, 2005, in two physical formats and for digital consumption, distributed by EMI Japan and EastWorld. "Passion", alongside its English counterpart "Sanctuary", were used as the national and international theme songs to the Square Enix video game Kingdom Hearts II (2005); the tracks serve as the successors to "Hikari" and its English counterpart, "Simple and Clean", which are found on Kingdom Hearts. The creator of the Kingdom Hearts franchise, Tetsuya Nomura, sought to collaborate with Utada as they previously wrote "Hikari", alongside his prospects for to break into foreign and international markets. The conception of the two tracks were to emphasize a "dusk"-like vibe to the game, in comparison to "Hikari" which they described as the "dawn". Musically, "Passion" has been described by music commentators as a multi-genre tune, noting elements of alternative rock, ambient and "ethereal" music. The song's lyrics delve into themes of nostalgia, and discuses the circumstances of past, present and future. Upon its release, both songs received critical acclaim from music critics, who strongly opined their musical departure and the Utada's progression in production and singing. Additionally, several publications ranked the songs on their year-end lists of 2005–06 and soundtrack lists. Commercially, "Passion" was successful in Japan, peaking inside the top ten on the Oricon Singles Chart and TBS's Count Down TV chart; despite this, "Passion"'s sales were much lower than previous releases. However, it was certified Gold in three categories by the Recording Industry Association of Japan (RIAJ). An accompanying music video was directed in China by their then husband Kazuaki Kiriya, which depicts Utada in a dreamscape filled with animated clouds, figures and a cathedral-like architecture. The clip was inspired by numerous anime films and aesthetics, along with the atmosphere portrayed in Kingdom Hearts II. The music video for "Passion" was generally well received, but critics questioned the lack of footage from the video game. In order to promote the single, Utada performed the tracks on television shows such as Music Station and Hey! Hey! Hey! Music Champ, and has appeared on one concert tour: Utada: In the Flesh 2010. Since its release, "Passion" and "Sanctuary" have been widely considered as two of the best songs in video game history and has been recognized as a major factor