Correlations exist based on common factors. When common factors cease, correlations cease.
My opinion is that common factors underpinning Nikkei225-¥en-U$-PM correlation are falling apart.
Over recent years the common factors operating & underpinning these correlations are:

1. ¥en use for risk-on carry trade.
2. Inverse relationship of stock prices to currency stocks are priced in.
3. Risk-off fear means move back into ¥en, which then rises.
4. Risk-on greed means move out of carry-trade ¥en, which then falls.
5. PMs (gold & silver) have generally parelleled the ¥en's risk-on, -off moves up & down.

There're now conflicting views, as ever in markets, about ¥en. Japan has the most insane QE & government debt levels, with BoJ holding insane amounts of gov'mt bonds & corporate paper. Elections are coming up. High levels of savings & investments by Japanese bolster ¥en. But North Korea situation may put Japan in danger - collapse of its insane QE paper-bandaged over sick economy & ¥en collapse? In that shituation some Nikkei stocks like Mitsubishi, involved in military hardware manufacture, may thrive & send Nikkei up. But Nikkei is more likely to collapse along with ¥en IF North Korea situation deteriorates into outright conflict, with possibly more nuclear fallout in Japan added to the nuclear power station disaster they're still suffering....
More serious conflict will almost certainly cause gold/silver prices to rise in ¥en & U$ terms.
Seems to me that a sharp breakdown of ¥en-Nikkei-U$-PM correlation is imminent as we move into end phase of QE, financial debt-Disneyland & U$ domination... with likely outbreak of more serious conflict. ¥en collapse as PMs soar & continued U$ collapse as world moves out of U$ into PMs & possibly into gold-backed Yuan & Ruble? Japan has been a U$ protectorate since WWII, and both ¥en & U$ are likely to get seriously hit by powershift towards China-Russia. Recent incidents with damage to US military in Pacific region indicate that US military aint as superior as they may think. US lost in Vietnam, and has affectively lost in Iraq and Syria, while US plans so far failed in Ukraine & E. Europe.
CONCLUSION: over coming years to 2025 I expect collapse of ¥en, most Nikkei companies, U$, most S&P companies, while gold & silver priced in those currencies will soar. IF China, Russia, others manage to back their currencies with PMs that will underpin their economies against hollow fiat of most Western states. This analysis is not likely to be more than 50% correct, because there are too many variables to take account of. But it would mean an irrevocable breakdown & TERMINATION of those correlations mentioned. Notably ¥en collapse versus Chinese Yuan & other currencies while gold soars. This is the total opposite of what pertained over recent decades!
Happy charting on the high seas of financial piracy!