Sunday USD/JPY is a weekend reference market for the number of yen per US dollar. It can move while the regular currency market is closed; it is not the official weekday USD/JPY closing rate.
Comparing charts on this board
Compare the weekend USD/JPY reference with regular USD/JPY to follow direction from Friday's close after weekend policy or geopolitical news.
After-hours Nikkei and S&P 500 CFD add an equity lens where quotes are available. Treat the weekend contract and weekday FX as separate markets, and complete the comparison with Monday's actual reopening.
Related charts: USD / JPY · Nikkei 225 CFD · S&P 500 CFD
Official references: Bank of Japan: FX statistics