The G10N Fugaku was a intercontinental bomber designed by the Japanese corporation, Nakajima Aircraft Company, during WW2 for the Z-plane program. It was to have 6 engines, have a stepless glass cockpit similar to the B-29, and would’ve used the northern jet streams to increase range and save fuel (almost same concepts as the Fu-Go balloon bombs). Due to numerous problems, such as rival bomber designs, the lack of resources and fuel needed for the Fugaku, the project was cancelled.
The K-go bomb which this plane carries was an actual nuclear project by Japan during WW2, though in real life the nuclear program never reached the levels the Manhattan Project did, AKA actually creating a usable bomb. (Ok, after some more research, I think the nuclear project was actually named F-go)
Also I am cooking up MUCH better than this thingy, but uhhh… procrastination. (I’ll give you a hint, Japan + A9/A10 Rocket)