The Shinyo was converted from the German passenger liner Scharnhorst which had been in Kobe harbor since 1939 since it couldn't go home. It was purchased in February 1942 by the Japanese government after the Battle of Midway.
As the IJN Chuyo had just been completed it was decided the conversion for the Shinyo should be very similar.
The steel used in the conversion came from the abandoned fourth hull, No. 111, of the Yamato class battleships.
To increase stability bulges were added.
The flight deck was flush. There were two elevators that took planes between the hangar and flight deck.