Nocturne follows a high school student in modern-day Tokyo, who is transformed into the demonic Demi-fiend after the world undergoes Conception, an apocalyptic event triggered by a sinister cult to enable the world's rebirth in a new form. With Tokyo transformed into a Vortex World filled with demons, the Demi-fiend becomes instrumental to the schemes of the Reasons, beings who seek to remake the world in their image, and Lucifer, the lord of demons. The gameplay uses a turn-based battle system based on exploiting weaknesses, and a Demon recruitment system allowing the player to recruit demons found in the Vortex World to fight alongside them.
The game was conceived after the completion of Shin Megami Tensei II and Shin Megami Tensei If…, but was delayed as the team worked out what they wanted for the game, including making it appeal to a wider audience than previous Megami Tensei games. Unlike the science fiction setting of Shin Megami Tensei II, Nocturne returned to a contemporary setting similar to the original game. The setting and characters were inspired by multiple elements, including Gnosticism, Mahayana Buddhism, and modern popular culture. Among the things the team changed from previous entries were the camera perspective, which was switched from a first- to a third-person camera perspective, and using a cel-shaded art style to distinguish it from other games of the time. The music, primarily composed by Shoji Meguro, paid homage to earlier Megami Tensei titles while drawing on music styles from the 1980s.
The original edition of Nocturne released in Japan to strong sales and a positive critical reception, and the limited director's cut proved so popular that Atlus made a second print in response to fan demand. It also inspired a drama CD and light novel in Japan. The director's cut was the version chosen for localization, making Nocturne the first mainline Shin Megami Tensei game to be released in the west. The game was well received by video game publications, who praised its gameplay and atmosphere, while its challenging difficulty was often a subject of criticism and occasional praise. It was also announced to have been a commercial success in the West.
The setting and events of Nocturne take place in a separate continuity to the rest of the Megami Tensei series.[13] Nocturne is set in modern-day Tokyo before and after an event called the Conception, in which the normal world is destroyed through the actions of a cult to prevent the world's stagnation and ultimate demise, as dictated by the Great Will governing existence. Tokyo is transformed into a wasteland on the inside of a sphere inhabited by the spirits of humans who died in the Conception; demons who wage war with each other; and Reasons, deity-like beings formed from the gathering of Magatsuhi by people with a deity or demon sponsor. Those who possess Reasons seek to remake the world in their image by presenting themselves to Kagutsuchi, a semi-sentient manifestation of the Great Will's power which exists to perpetuate the destruction and rebirth of worlds through Conception, and proving their worth.[Quote 1] Another realm mentioned in the story is the Shadow Vortex, a limbo where dead worlds and the beings who created them linger.[14]
The nameless main Protagonist is the player character: generally dubbed the Demi-fiend, he is an "everyday man" who represents the player. Several other characters survive the opening events of the game alongside him, many of them representing the various routes the player can choose to take. They are Yuko Takao, his teacher and a key figure in future events; his classmates Chiaki Hayasaka and Isamu Nitta; and Hikawa, leader of the Cult of Gaea and later the Assembly of Nihilo. Other characters include Jyoji Hijiri, a journalist the Protagonist meets with prior to the Conception; and Futomimi, a powerful Manikin seeking to create his own Reason. All the game's events are watched over by Lucifer, ruler of the demons and the Great Will's sworn enemy, who takes on multiple forms during the story.[14] Two characters from other games are included in later versions. These are demon hunter Dante from the Devil May Cry franchise; and Raidou Kuzunoha, a lead character from the Shin Megami Tensei: Devil Summoner subseries.[15][16]
The game begins with the Protagonist arriving in Tokyo to meet up with Chiaki and Isamu to visit Takao in a hospital. While in the city, the player learns of a confrontation between two cults which resulted in several deaths, and learns details of it from Hijiri when he meets them in the park where the event took place.