In Sonic Adventure 2, Sonic is arrested by the Guardian Units of Nations military organization due to being the supposed perpetrator of a Chaos Emerald theft. Sonic Adventure 2 additionally serves as the debut of Shadow the Hedgehog, a black hedgehog that vaguely looks like Sonic, and Rouge the Bat, an enigmatic treasure hunter. The game features two good-and-evil storylines, each featuring three playable characters with whom they share a gameplay style with their opposite counterpart. It is the sequel to Sonic Adventure and was developed to celebrate the tenth anniversary of the franchise, as well as the last Sonic title to be released on a Sega console. Sonic Adventure 2 ( ソニックアドベンチャー2, Sonikku Adobenchā Tsū ?) is a platform game developed by Sonic Team and published by Sega in 2001 for the Dreamcast, as part of the Sonic the Hedgehog series.