Dont quote absurd numbers, the Japanese did not kill 30 million, they did not kill even a million, more likely, under 100,000.
Total WW2 casualties was 60 million and you come with you wisdom and say the Japs killed 30 million Chinese, my foot.
R. J. Rummel estimates the civilian victims at 5,424,000. Detailed by country: China 3,695,000; Indochina 457,000; Korea 378,000; Indonesia 375,000; Malaya-Singapore 283,000; Philippines 119,000, Burma 60,000 and Pacific Islands 57,000.
Rummel estimates POW deaths in Japanese custody at 539,000 Detailed by country: China 400,000; French Indochina 30,000; Philippines 27,300; Netherlands 25,000; France 14,000; UK 13,000; UK-Colonies 11,000; US 10,700; Australia 8,000.[8][56]
Werner Gruhl estimates the civilian victims at 20,365,000. Detailed by country: China 12,392,000; Indochina 1,500,000; Korea 500,000; Dutch East Indies 3,000,000; Malaya and Singapore 100,000; Philippines 500,000; Burma 170,000; Forced laborers in Southeast Asia 70,000, 30,000 interned non-Asian civilians; Timor 60,000; Thailand and Pacific Islands 60,000.[57] Gruhl estimates POW deaths in Japanese captivity at 331,584. Detailed by country: China 270,000; Netherlands 8,500; U.K. 12,433; Canada 273; Philippines 20,000; Australia 7,412; New Zealand 31; and the United States 12,935[57]
The historian Chalmers Johnson has written that "the Japanese slaughtered as many as 30 million Filipinos, Malays, Vietnamese, Cambodians, Indonesians and Burmese, at least 23 million of them ethnic Chinese[58]
Out of "60,000" Indian Army POWs taken at the Fall of Singapore, 11,000 died in captivity[59]
If you include the people who indirectly killed by Japanese because of the Invasion, then 30 million number justified.