In all probability, it would be a Ki-45-KAI. Perhaps one of the several other versions such as the Ki-45-KAI-Ko or the Ki-45-KAI-Hei. These were the primary twin-engine fighters involved in intercepting B-29s. The Japanese Navy flew some J1N1-S Gekkos against the B-29s, but the Army Ki-45s were far more numerous.
My regards,
Widewing