Japan’s 4% bond yield spike threatens the low-cost borrowing strategy behind corporate Bitcoin buying

Japan’s 30-year government-bond auction cleared at a 4.079% average yield on Sept. 3, underscoring a tougher backdrop for future capital raised by Metaplanet to buy Bitcoin. The long bond is a market signal; the nearer test for the company is the price of shorter-tenor debt and refinancing.The average yield rose 14.2 basis points from 3.937% at the previous 30-year auction on Aug. 6. Japan’s Sept. 1 10-year auction averaged 2.995%, placing the 4% threshold at the long end rather than across the entire curve. The Bank of Japan, meanwhile, maintains an operating guideline of around 1% for the uncollateralized overnight call rate.Metaplanet’s existing fixed obligations retain their contractual cash flows. Its ¥8 billion 20th-series ordinary bond is zero-coupon and matures on April 23, 2027, while its inaugural BitBonds carry fixed coupons. The shift in Japanese yields instead raises the benchmark for future issuance and refinancing.That leaves a narrower version of Metaplanet’s funding advantage intact. The bilateral zero-coupon bond protects near-term cash flow, but repeating such favorable terms at the scale required for sustained Bitcoin purchases remains uncertain.Metaplanet BitBo...