After what China did to Japan 500 years ago (under Mongol rule) (not Mongol rule as a hexbearer pointed out actually), they have no right to condemn Japan for anything; also bacteria, viruses, what’s the difference? Also it was an attack, not an epidemic that formed naturally like they have throughout history.
Like seriously they chosen that? Just one carpet bombing by USA killed more Japanese people than both invasions together. Few years of Japanese wako raids killed more people in China than those invasions. Hell, those invasions, according to the Hojo regent, didn’t killed enough people since after them, the government went into serious crisis because there was not enough money and land to reward the participating warriors.