On 8 January 1945, one of the two J8M1 prototypes was towed aloft, water ballast added in place of the fuel tank and rocket engine to test its aerodynamics. The test flights confirmed the design. Training courses for JAAF and JNAF pilots began on the Ku-53 glider, which shared a similar configuration to the J8M1. The 312th Naval Air Group was selected to operate the first J8M1. Mitsubishi, Fuji Hikoki, and Nissan Jidosha all had tooling for mass production well into the advanced stages, ready to produce both the J8M1 and the J8M2 variant, which differed from the J8M1 in sacrificing one of the Type 5 cannon for a small increase in fuel capacity. The first J8M1 prototype to be equipped with the Toko Ro.2 (KR10) was ready in June 1945. They were then transferred from the Nagoya plant to Yokoku for final checks before powered flight testing, after final glide tests with the engine installed.