Be With You (2018)

Soo-Ah, before passing away makes an unbelievable promise to her husband, Woo-Jin, to return one year later on a rainy day. Miraculously, she keeps the promise and reappears before her husband and son but all her memories have disappeared.

Tragically, the relief at their reunion is short-lived, because it turns out that Soo Ah has to leave her family once again.