With no time to lose, Sonic and Tails head for ground zero to retrieve the stolen gem. Without the power of all six Chaos Emeralds, South Island and its residents will sink into the ocean. As a result of the theft, the other five Emeralds have been thrown off-balance, scattered to all ends of the island. While out on an aimless adventure, Sonic and Tails hear a troubling rumor: word has it that Robotnik has returned to South Island in their absence and has managed to procure the Red Chaos Emerald. Robotnik and his quest for world domination via the use of the mysterious Chaos Emeralds to create nuclear weapons and lasers (according to the North American instruction manual). The storyline to Sonic Chaos revolves around Dr. Sonic Chaos is notable for the fact that it is the first 8-bit Sonic title to feature Tails as a playable character, and also the first in the series to allow the player to manually control his flight. It was the last platform based Sonic game released for the European Sega Master System.

It was later released for the Sega Game Gear in Japan on Novemunder the name Sonic & Tails (ソニック&テイルス Sonikku to Teirusu?), on Novemin North America under simply Sonic Chaos and in Europe in November 1993 under the same name. Sonic the Hedgehog Chaos is a platform game for the Sega Master System developed by Aspect and published and released by Sega in Europe on October 25, 1993.

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