Japan's Bond Market Is Still Breaking. It Just Got Worse.
Author: Protik Ganguly
In early 2026, we wrote that Japan's bond market had broken and your mortgage felt it. The situation has deteriorated further. Japan's 10-year government bond yield has climbed to 2.8% — a level not seen since 1997. The 30-year yield hit 3.95% — a record high. The mechanism connecting Tokyo to your financial life is running faster than before.
The original story was about a crack. This is about what happens when the crack widens.
Japan sold nearly $30 billion worth of US crude to the Treasuries in the first quarter of 2026 alone — the fastest pace of selling in four years (Indmoney, 2026). The logic is straightforward: for the first time in a generation, Japanese investors — pension funds, life insurers, banks — can earn meaningful returns at home in yen, without taking currency risk by parking money in US Treasuries. When Japanese money stops flowing into US bonds, US bond prices fall. When US bond prices fall, yields rise. When yields rise, mortgage rates follow. The mechanism is the same. The scale has changed.
The yen carry trade — the decades-old practice of borrowing cheaply in Japan and investing in higher-yielding assets globally — is unwinding. As Japanese yields rise, the cost of the trade increases. Investors who borrowed yen must buy yen back to repay loans, which strengthens the yen, which makes the trade more expensive, which triggers more unwinding (Indmoney, 2026). The self-reinforcing spiral runs in reverse exactly as it ran on the way in. Societe Generale's global strategist described the potential outcome as "a loud sucking sound in US financial assets" (CNBC, 2026).
The Bank of Japan raised its policy rate to 0.75% in December 2025. Markets in June 2026 are pricing in a 78% probability of another hike to 1.0% (Trading Economics, 2026). Each hike makes Japanese bonds more attractive relative to US Treasuries. Each marginal improvement in relative attractiveness is another reason for Japanese capital to come home.
Japan's Prime Minister has approved a $19 billion supplementary budget to support households struggling with Iran-conflict-driven energy costs. The bond market's response was immediate. One analyst noted: "Bond markets are a lot of things, but they're not stupid. You cannot increase spending without increasing debt" (CNBC, 2026).
The direct connection to your mortgage rate remains what it was in January: US 10-year Treasury yields set the floor for 30-year fixed mortgage rates. When Japanese capital stops buying US Treasuries — or starts selling them — that floor rises. The 30-year fixed mortgage rate has not fallen meaningfully despite Federal Reserve pressure because the global bond market has other ideas. Japan is a significant reason why.
This is not a prediction of collapse. It is a description of a mechanism operating in real time, at increasing intensity, in a direction that is not favourable for US borrowing costs. The crack that formed in January has not closed. It has grown.
References
Indmoney. (2026, May). Japan carry trade unwind: What it means for investors in 2026. https://www.indmoney.com/blog/us-stocks/japan-yen-carry-trade-unwind-market-impact
Oxford Economics. (2026, April 28). The BOJ will continue raising rates in Japan, but the pace is highly uncertain. https://www.oxfordeconomics.com/resource/the-boj-will-continue-raising-rates-in-japan-but-the-pace-is-highly-uncertain/
Trading Economics. (2026, June). Japan government bond yield. https://tradingeconomics.com/japan/government-bond-yield
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