Naoto Ohshima

From Sonic - Wiki on Neoseeker

Naoto Ohshima is a former SEGA employee, famed for creating Sonic the Hedgehog and Dr. Eggman for the first game on SEGA Genesis. Ohshima gained renown at SEGA's Sonic Team for creating characters and playing integral roles in the development of games like Phantasy Star, Sonic CD, Nights into Dreams... and Sonic Adventure.