Sigma Harmonics

Sigma Harmonics is a role-playing video game in which players take on the roles of Sigma Kurogami and Neon Tsukiyumi, who go on an adventure requiring them to travel through time using an artifact called the Great Clock. The entire game takes place within Kurogami Mansion, which is portrayed in-game with 2D pre-rendered backgrounds on which 3D models appear. The game, split into several chapters, is played using the Nintendo DS's book orientation; the top screen displays illustration-style cutscenes and battle sequences, while the touch screen is used for issuing commands and completing other gameplay segments. In the room of the Great Clock, Sigma can initiate his Time Spin power, going both between timelines and to different points within a timeline. These different times are represented with illustrated cards.

During exploration and its associated adventure segments, the player controls Sigma as he explores Kurogami Mansion. Using black monuments in the environment, Sigma can relive the events of the crime within that area, discovering events and unlocking clues. Sigma can also stand in environments and scan for additional information, which take the forms of medals representing a clue. When enough clues are assembled, Sigma can trigger the Superdeduction system, his mental image of the case represented with a grid containing black nodes symbolizing key aspects of the mystery.

Sigma Harmonics is set in an alternate version of Tokyo. In ancient times when the gods overtly influenced humanity, demonic forces terrorised the world. The gods empowered some human families with magical abilities, dubbing them as "Servants". These Servant families successfully sealed the demons, using an artifact called the Great Clock as the lock.

The entire scenario takes place in the Kurogami family mansion, which changes depending on the time period and current events. A key mechanic and plot point is the alteration of time by killing someone, causing a ripple effect forward through time.

Sigma Harmonics was co-developed by Square Enix and Think Garage; the Square Enix staff members had previously worked on Dirge of Cerberus: Final Fantasy VII, while Think Garage had worked with Square Enix on Dragon Quest & Final Fantasy in Itadaki Street Portable. Hiroki Chiba acted as director and writer, Yoshinori Kitase was producer, and Yusaku Nakaaki was the project's lead artist. It was Chiba's second project as a director, the first being Dynami Tracer for the Satellaview in 1996. Production took roughly two years, said to be long for a DS title, and had a fairly small staff number and budget compared to the company's work on the Final Fantasy series.

The game was conceived by Chiba while the team were still providing online support for Dirge of Cerberus. His initial pitch to Kitase was a game that fused mystery adventure with the company's established RPG design.

The game debuted on the Japanese sales charts at number 8, selling 23,000 units. It was only one of three new entries in the charts that week. As of September 2008, the game has sold 70,000 units in Japan, ranking among Square Enix's best-selling titles for that year from new IPs.

In a preview of the game, John Tanaka of IGN noted the unconventional design of the battle system. Jeremy Parish, writing for 1Up.com, positively compared the game to The World Ends with You and said that its blending of genres gave Sigma Harmonics "a distinctly unique feel".