Japanese design initiated in late 1942 as a ground attack aircraft, by 1944 the pressure of US strategic bombing had changed priorities and it was reworked as a high altitude fighter with a larger, turbocharged radial engine. I am uncertain which version of the design this model represents as detailed information is hard to find in English. From the relatively short and simple design of the wings I would guess it is the original low-altitude version.
Revised (31-Jul-2013) with shorter/thicker guns.