So because they didn't know they get off the hook? And If you are talking about Europeans wrecking Africa shouldn't you being taking this up with the EU?
If the world outside the West(including Japan as the West here) were to demand reparations for the abhorrent actions taken by Western states in the past five centuries the West would be composed of nothing but paupers. That's why we don't do it. It's foolish at this point in time and would cause more harm than good. Not to mention that the most realistic outcome of such a demand would be a worthless apology for past actions and an absolute refusal. Still, outside of Islamic extremism I'm frankly surprised that there aren't more post-colonial states clamoring for a break with the West for their past actions....but money.
Take me being Peruvian, for example. On paper, I should loathe the Spanish for ruining the demographic health of the Andes region and causing mass depopulation by turning the natives into meat for the grinder that was the mines of Potosi. Without mentioning centuries of criminal negligence, dividing the Incan Empire into several bickering nations, exploitation, mass resource extraction, slavery of natives, destruction of a culture, instigation of a rigid racial social hierarchy and a complete lack of reinvestment in the lands I'm from as well as setting up local oligarchs that would ultimately lead my country down a path of impotence vis a vis other states for most of its post-colonial history. Well, I guess that's not entirely accurate. I suppose they'd have viewed it as a favor that they brought us Jesus. /s
But the truth is that the Spanish people of today were just as much victims of their fuckwit monarchs and greedy nobles from four centuries ago as whatever ancestors I have were, ignoring the whole 'I know for a fact that a conquistador's blood runs in my veins' thing. Because only fuckwits could turn the Spanish Empire of Charles V into a second rate power by the time of the Enlightenment and a non-factor by the end of the Napoleonic Wars that has undoubtedly made Spain far poorer, less prosperous, and less successful than it has any right to be for a nation with access to as many markets, lands, and resources as it did. Spain's seen suffering too from the Napoleonic invasion of Spain utterly decimating the demographics, economy, and stability of the nation to the Spanish Civil War's destructive effects that were undoubtedly apparent in the social fabric of the Spanish until well into the 80s and 90s that left Spain as a developed economy.
The only nations to truly stay 'winning' in spite of their actions are Great Britain and the USA, if we're being honest. But I can't see it being plausible or palatable for reparations towards anything outside of a generous affirmative action stimulus package.