The Caligula Effect: Overdose

The Caligula Effect is a role-playing video game featuring turn-based combat in dungeon environments. Combat is triggered upon encountering enemy characters during dungeon exploration. A party can consist of four playable characters maximum. There are 9 main characters that can be used in the party as the story progresses.

Any NPC can be recruited into the party after obtaining level 2 or higher association. Three commands can be chained together per turn for each party member and can preview its effect before initiating. Players can raise association with other NPCs by interacting with them. Certain NPCs are not accessible until specific NPC association is gained.

The Caligula Effect is set in a virtual reality program known as "Mobius", created so people can escape pain in their lives within reality and live in an idyllic high school setting, forced to live out their 3 years indefinitely. The main protagonist is one of the group who realizes that they are in a virtual world, and ally with the former keeper of Mobius, "Aria" to form the "Go-Home Club", a group dedicated to escaping from Mobius and its god-like overseer program, a vocal program called "μ". They oppose the "Ostinato Musicians", a group who supports μ and sees the Go-Home Club as traitors.

The Caligula Effect was developed by FuRyu and published worldwide by Atlus USA. It was directed by Takuya Yamanaka, with character designs by Oguchi. It was written by Tadashi Satomi, who had previously worked on the first three games in the Persona series – Revelations: Persona, Persona 2: Innocent Sin and Persona 2: Eternal Punishment. The music was written by former Megami Tensei series composer Tsukasa Masuko, and the theme song is performed by a three-person group: Eriko Nakamura, Emi Nitta and Yuka Ōtsubo. The developers define Caligula as a "next-generation juvenile RPG" focusing on modern pathology and trauma.

The characters were said to violate a variety of taboos, with Satomi specifically creating one that the team were initially wanting to avoid. The title stems from the psychological term "Caligula effect", referring to the want to see and do prohibited things. Despite its prominence and tying into the gameplay experience, the word itself is not mentioned within the game's context.

The Caligula Effect received "mixed or average reviews" from critics, according to review aggregator Metacritic. Famitsu scored the original version of the game with a 30 out of 40 rating, with an 8/7/8/7 out of 10 breakdown among the four reviewers. Josh Tolentino from Destructoid gave the game 4/10, praising the fresh idea and the battle system of the game, but criticized the shallow character bonding system, the long length of battles and the poor performance of the game on the PlayStation Vita.

The remake fared better among reviewers, with Famitsu giving it with a higher 33 out of 40 score, consisting of ratings from four critics who individually gave it 9/8/8/8.