[Pursuivant]

Like Major.Kudo says.

FWIW, Francillon says that an unspecified number of Ki-45 (probably of what he calls the Ki-45KAIb block) were field modified to carry oblique firing cannons. That's the field modified nightfighter version in my chart.

The conversion proved successful, so some or all of the next production block were built as night fighters.

The next block after that was built as an anti-shipping version, but some were also fitted as night fighters.

If you've trying to create night fighter variant of the Ki-45, I think that you've got five options:

Field modified Ki-45 Ko (possibly Otsu), possibly with rear MG
Ki-45 Hei early with 2 x Ho-103 cannon, possibly with rear MG
Ki-45 Hei late with 2 x Ho-5 20mm cannon, no rear MG
Ki-45 Tei (modified from Hei) as Tei, but no nose guns, 2 x Ho-5 20 mm cannon in oblique mount.
Ki-45 Tei (modified from Hei) as above, but TaKi-4 centimetric radar installed in nose.

Of the list above, I think that the "definitive" Ki-45 night fighter version would probably be the Ki-45 Hei late production block, without radar.

But, my understanding is that there were many field mods to the Ki-45 since it was such a versatile aircraft, and because isolated IJAF units had to improvise. So, any night fighter variant of what IL2 calls the Otsu, with 2 oblique-mounted Ho-103 or Ho-105 cannons, will probably be realistic, or at least "realistic enough."