The yen went 164 to 155 and back to 157 in a week — the first US-Japan coordinated yen-buying in 28 years. How should HK buyers do the maths?

In late July the dollar hit 163.988 yen, the weakest the yen has been since 1986. The market saw Japan intervening on successive days from 30 July to 3 August, and the officially confirmed 31 July action was the first coordinated US-Japan yen-buying since 1998 — the rate snapped back toward 155 before easing to above 157. On the same ¥30M property, the Hong Kong dollar cost swung by some HK$80,000 in a week. But the real task isn't forecasting the rate; it's deciding how you lock your numbers.