Who Made Sonic the Hedgehog?

I'd been wondering who made Sonic, and if it was Yuji Naka. After doing research, he was credited as the Programmer of Sonic, but not the Designer - which only furthered the mystery. I decided to do a deep dive and try to find out Who Made Sonic the Hedgehog, and I hope you find it as interesting as I do!

Sources:
Sega Mega Drive/Genesis Collected Works - Keith Stuart
Retro Gamer: Issue #100
Sonic the Hedgehog - GameTap Retrospective (2009)
Naoto Ohshima interview (Gamasutra): http://www.gamasutra.com/view/feature...
The History of Sonic: Birth of An Icon (Documentary)

Music List:
0:00 - Sonic CD - Sonic Boom
0:51 - Sonic 3 - Angel Island, Act 1
1:29 - Alex Kidd in Miracle World - Main Theme
1:50 - Sonic 2 - Metropolis Zone
2:10 - Sonic (Master System/Game Gear) - Scarp Brain Zone
2:59 - Phantasy Star - Lashiec FM (JP version)
3:52 - Sonic 06 - Dusty Desert Quicksand
5:04 - Sonic 3 - Hydrocity Zone, Act 1
6:05 - Sonic 2 - Hill Top Zone
6:36 - Emerald Hill Zone
7:00 - Sonic - Green Hill Zone
8:23 - Sonic 2 - Chemical Plant Zone
8:53 - Sonic 3 - Death Egg Zone
9:09 - Sonic Adventure 2 - Escape from the City
9:38 - Sonic 2 - Mystic Cave Zone