"Shin Megami Tensei: Digital Devil Saga, known in Japan as Digital Devil Saga: Avatar Tuner is the first of two games in the Digital Devil Saga games. It was released in Japan in 2004 and in North America the next year, being released again in the PAL region in 2006. Digital Devil Saga differs from other Megami Tensei games in that the player cannot summon demons, but must utilize a party of characters and their demon transformations. Shin Megami Tensei: Digital Devil Saga 2, known in Japan as Digital Devil Saga 2, is a direct sequel to the first game. It was released in 2005 in both Japan and North America and in 2006 in the PAL region.
This series is one of the many Spin-off series of the Megami Tensei."
Source: Wikipedia, "Megami_Tensei", available under the CC-BY-SA License.