THE MOST DANGEROUS MARKET IN THE WORLD RIGHT NOW IS JAPAN. Japan's 10 year and 20 year bond yields just hit 30 year highs. Both moved to their highest levels in three decades. The 10 year yield is up 137 basis points over the past 12 months, and up another 9.1 basis points in just the last 4 weeks. The move is accelerating, not slowing down. 1. 10 year JGB yield: 30 year high 2. 20 year JGB yield: 30 year high 3. 10 year yield: +137bps over 12 months, +9.1bps over 4 weeks 4. 20 year auction demand: weakest since the May 2025 rout 5. Yen: trading near 40 year lows 6. Japan debt to GDP: over 200% 7. Japan foreign reserves: over $1 trillion, 2nd largest in the world Two things are happening on the supply and demand side at the same time. On supply, Tokyo just announced a plan to mobilize over ¥370 trillion ($2.29 trillion) in public and private investment through fiscal 2040. That means more bond issuance ahead. On demand, the Bank of Japan is the buyer stepping back. The BOJ is tapering its JGB holdings, targeting a reduction to about ¥480 trillion by March 2027, roughly 17% below its June 2024 level. That's the largest buyer of Japanese debt pulling back exactly when new issuance is rising. Private banks can't fully absorb the gap. Japanese megabanks run an average bond duration under 2 years, well short of the 9.5 year average maturity of outstanding JGBs. That mismatch is a structural reason the 20 year auction just saw its weakest demand in over a year. Less demand at auction plus more supply plus a smaller BOJ bid means yields get pushed higher mechanically, not just sentimentally. At the same time, the yen near 40 year lows is pushing the BOJ toward higher rates to defend the currency, which conflicts with keeping borrowing costs low for the government's spending plan. Japan holds the largest foreign reserve stockpile in the world and has funded cheap borrowing globally for years through near zero rates. If Japanese yields keep climbing, capital funded by cheap yen borrowing and parked in higher yielding assets abroad has more reason to come home. That's the yen carry trade unwinding, and it's one of the direct channels through which Japanese bond stress spreads into global risk assets.