It has everything to do with humanity
Japanese may be business partners but they are not admired respected or trusted - nor do they return those innate feelings to other Asians, being proud haughty and xenophobic
They have no reputation as “humanitarians”
Its a bit remarkable the US has been able to build a military coalition willing to defend Japan from China
Korea and China would more naturally form against a resurgent Japan, given what they suffered from Japan throughout history
Other than business realities and the US presence as a centrifying force to keep the Pacific open for trade and shipping, I doubt the people of SEA, RP, Singapore and Australia see Japan as a noble culture for the same reason
“Its a bit remarkable the US has been able to build a military coalition willing to defend Japan from China”
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Eisenhower government forced Japan to accept the coalition proposal. It was extremely unpopular, sparked left leaning anti-war mass protests. PM Kishi (he used to be class A War criminal suspect) took the great risk to sign the Japan-America security treaty and resigned. Pro-China socialist party would have won the election, if its leader hadn’t been assassinated by a far-right activist.