Twilight Syndrome (トワイライトシンドローム) is a series of horror adventure games developed by Human Entertainment and, later, Spike (now Spike Chunsoft). The first three games in the series were directed by Goichi Suda; after he departed Human and formed Grasshopper Manufacture, the series continued without him with mostly unrelated stories. However, the characters and setting of his Twilight Syndrome games continued to be referenced in The Silver Case and further games, making up the universe known as "Kill the Past".
The series revolves around high school girls investigating paranormal urban legends around their school and town. In Suda's original entries, the cast and setting of the three games is consistent, always starring Mika Kishii, Yukari Hasegawa and Chisato Itsushima, and taking place in Hinashiro City. In further entries in the series, the casts and settings are different, although the original games are occasionally referenced.
- Twilight Syndrome: Search (1996)
- Twilight Syndrome: Investigation (1996)
- Moonlight Syndrome (1997)
- Twilight Syndrome: Reunion (2000)
- Twilight Syndrome (mobile phone game) (2001)
- Twilight Syndrome: The Forbidden Urban Legend (2008)
- Twilight Syndrome: Graduation (2000)
- Twilight Syndrome: Dead Cruise (2008)
- Twilight Syndrome: Dead Go Round (2008)
Twilight Syndrome was inspired by an unreleased internal prototype at Human called Grandish Manor, which was a horror audio experience meant to be listened to with headphones. Because it was popular with the staff, they decided to develop a horror adventure game.
The original Twilight Syndrome duology was intended to release as one game. After a good amount had already been written, the previous director quit the project, and Suda was brought in to finish the game. During development, it was found that what had been written up until then wouldn't fit on one disc, and it would have to be a two-disc game. Rather than simply split the content between discs, though, the team elected to fit what they could on to one disc, which was released as Search. They then took the rest of the content and wrote new material, doubling the length, and released it later the same year as Investigation. The games are still intended to be played together; the secret final chapter of Investigation can only be unlocked by having 100% save files from both games on the player's memory card.
This secret chapter leads the duology into Moonlight Syndrome, which Suda was involved with from the beginning; thus, it took on a much more dark and experimental tone, while still following directly from the previous Twilight Syndromes. It was after this that Suda left with some of the Syndrome staff to form Grasshopper Manufacture, where he continued developing ideas from his Syndrome games. However, the series returned three years later when Spike received the rights to Twilight Syndrome from the bankrupt Human. Spike developed Twilight Syndrome: Reunion as a return to the less dark tone of the first two games, seemingly ignoring the continuity of Moonlight Syndrome and introducing a new cast and setting. Reunion also features more slice-of-life elements. It was succeeded by a movie, Twilight Syndrome: Graduation, and a mobile phone game.
In 2008, Spike revisited the series once again with Twilight Syndrome: The Forbidden Urban Legend on the Nintendo DS, which featured another cast of new characters and an aesthetic inspired by the original duology. More films and novels in the franchise released around the same time.
In fellow Spike Chunsoft game Danganronpa 2: Goodbye Despair, the Twilight Syndrome series is very explicitly referenced as a vital plot point when the primary antagonist Monokuma develops a fangame of the series entitled Twilight Syndrome: Murder Case, which the characters (and therefore player) have the opportunity to play. The graphics, gameplay and story are all made to resemble the original duology, and the game is vital in solving a murder mystery within Danganronpa 2. The characters Chiaki Nanami and Nagito Komaeda both state themselves to be big fans of the original series, and react negatively to the evil Monokuma associating himself with it. This is referenced again in the anime Danganronpa 3, with the caption "beginning of the twilight" appearing when the show begins to go over the events that inspired Monokuma's fangame.