In 1:72 the Fine Molds kit is the best around and available.
It has been released in two different boxes, the older suggesting gray for the lower surfaces.
The one released in 2001, code FP23, recommended prototype orange for the lower surfaces and is available through our on-line store.
Other more exotic kits were the one released by CMK which was resin and home-made. Didn't include any decals and the resin (with the occasional bubble) was so soft it melted with the summer heat.
And finally the Eagles vacform which had a pretty accurate shape but it gave only seats for the interior and no decals.
In 1:48 the only known kit was the resin released by Raccoon Models, code MPRCC4843. Extremely rare as all Raccoon Model kits are.
In 1:700 Pit Road has released two sets of metal planes. One called "Nihon Kaigun Tokushu Kogekiki" (IJNAF Special Attackers) code SP-53 which includes four Nakajima "Kikka" and two "Keiun".
And the set named "Nihon Kaigun Keikakuki Seto" (Japanese Navy Experimental Plane set), code MP-62, which includes two "Keiun", three "Kikka" and three "Shusui".
In 1:144 the ANiGRAND resin kit of Nakajima G5N1/2 "Shinzan" (Liz), code AA-4037, includes one Kawasaki Ki-78, one "Zuiun" and one "Keiun".