Yen movement and Nikkei 225 index have a clear positive correlation since 2002 (In this chart, Yen's upward movement suggests depreciation), because:
1. Exports and corporate profit benefit from depreciation of Yen, pushing stock prices up.
2. Interest rate is extremely low in Japan, so the financing costs of Yen are low, too, and traders like to borrow Yen to invest. Whenever the market is panicking due to economic tensions, Nikkei 225 index slides, and demand for Yen increases, because traders have to buy Yen to pay back their loans. Funds returning to Japan brings up Yen, and Nikkei 225 drops.
Nikkei 225 Index (L)2021-04-1929,685.37