Also known as: ソニックライバルズ
Sonic Rivals is a 2006 side-scrolling platform game in the Sonic (Series) series developed by Backbone Entertainment for the PlayStation Portable. It is notable for introducing Silver The Hedgehog's current main series incarnation, as opposed to the Silver featured in the alternate timeline bad future seen in Sonic The Hedgehog (2006).
This game is also noteworthy as being one of the few Sonic games that has never seen a release in Japan, along with it's sequel, Sonic Rivals 2.