Question re: Japanese Cargo Plane Type

Hello- I distinctly recall once reading about a Japanese tanker-type aircraft developed near the end of the war that reached the ultimate in absurdity: To fly to Burma and back to Yokosuka required *more* fuel than the plane could carry! This was by when the incredible US submarine force had completely sealed off the sea lanes to the Home Islands.
No matter how I phrase this on Google, I get nothing. It's driving me crazy. Help, please!

 

Kawanishi KX-03, a Spruce Goose on steroids. Never left the drawing board.