There was a documentary on History, Discovery, or NGeo about this some years ago. Remember, that the Japs got the jet and missile tech from their ally Germany, which they developed further than the Germans.
I believe the Japanese only had one or two prototypes flying in the July 1945 timeframe. They ordered 200 jets and no telling when they would have been combat ready. With the invasion set for March 1946, I doubt they would have been very effective at all against the invasion force.