Shortround6
Major General
Japanese were not taking the advantages of their 2-engined fighters as much as it was the case for the Western types. Neither Ki-45 nor J1N were adopted to carry some meaningful bomb load like it was the case with Bf 110 or P-38.
In some cases the Japanese were 1 to 2 years behind. It took a considerable amount of time to get the Ki-45 sorted out. The Ki-45 was also hindered by it's guns and the distances the JAAF wanted to fly.
Compare the Ki-45 to the Bf 110C. The Ki-45 had two 12.7mm mgs to the 110s four 7.9 guns. Germans did stuff 1000rpg in which was a little excessive. Germans were using the MG/FFM cannon like the ones in the Zero, JAAF didn't have them. They used a heavy 20mm gun that was rather slow firing.
From an aircraft designer point of view they put in close to the weight of armament that the 110 used (perhaps a little light on ammo). The guns chosen were not as effective as wanted but that is the Armies problem. They are the ones providing the guns.
The Ki-45 was finally provided with a pair of 250kg bombs, but the 110 only got to carry a pair of 250kg bombs with the C-4/B version which got DB 601N engines, The C-7 got the pair of 500kg bombs but got a stronger undercarriage. As the engines were upgraded in power the 110F came into service with DB 610Fs. Wing racks were into introduced for small bombs.
with the 110G and the DB 605 engines you could put some big bombs on the 110. Meanwhile the Ki-45 was stuck with same Ha-102 engine it had stared it's service life with in early 1942. granted this was a significate improvement over the 9 cylinder scaled down Mercury engines it started with.