Sonic the Hedgehog has found himself living through the events of Persona 3, in the alternate timeline 'Sonic Robo Blast 2 Persona'. He joins other characters from his universe; including Tails, Knuckles, Amy Rose, Shadow, Blaze, Silver, and even Dr. Eggman and Metal Sonic; that have found themselves inside the enigmatic tower Tartarus during the Dark Hour. He must face these challenges and Shadows before him with determination and a willingness to protect his friends and the world.