The once self-contained encryption circle has now become a barometer of global capital flow.

On December 15th, Bitcoin plunged from its high of $90,000 in the early morning. Within less than two hours of the Asian market opening, this digital asset dropped straight to the $85,000 mark, with a daily decline of over 5%. Traders sighed in various communities - here we go again.

Interestingly, traditional safe-haven asset gold remains completely unmoved. There have been no negative news reports, nor any explosive news, and there are no signs of large holders selling pressure on the blockchain. Where exactly is this silent sell-off coming from?

The answer points to Tokyo. The Bank of Japan plans to raise interest rates to 0.75% on December 19, the highest level in 30 years. A policy decision that seems distant can trigger a chain reaction of Bitcoin in the global market.

**The Invisible Financial Pipeline**

To understand this chain of cause and effect, we must start with a game that has lasted for a full thirty years—Yen arbitrage trading.

Japan has long maintained a near-zero interest rate policy, what does this mean? Borrowing yen costs almost nothing. Global hedge funds and asset management institutions are targeting this opportunity, borrowing yen from the Bank of Japan and then converting it into dollars to buy those assets that can really make money. US Treasuries, US stocks, Bitcoin... the higher the yield, the more attractive it is.

In simple terms, it can be summarized in four words: borrow cheap, buy expensive.

The direct scale of this operation is as large as several trillion dollars, and with leverage amplifying it, the overall amount is astonishingly large. This massive capital ultimately flows into U.S. Treasuries, European bonds, emerging market stocks, venture capital funds, and of course, encryption currencies. For a full decade, this "perpetual motion machine" seems to never stop — the lower the interest rates, the greater the arbitrage opportunities, and the crazier the capital becomes.