 Naka 's relationship with Sega of Japan was tenuous during this time ; he received little credit for his involvement in the game . He left the company shortly after the game 's release , although Sega of America hired him later . Before leaving , however , he defied Sega of Japan 's prohibition of developer credits by displaying a few names in black text on a black background , identifiable only by looking at the game 's code . 
