Ye Zhen suffers from Rainstorm Syndrome—a rare condition that causes her memories to rewind by one year whenever it rains, returning her to the day she made a promise with a certain man.

In her search to reclaim what she has lost, Ye Zhen becomes entangled with Jiang An, the enigmatic owner of a bookstore. Cold and distant, he is a man shrouded in lies and secrets—yet he never stops watching over her. His strangely familiar face leaves her restless, as if it holds the key to memories she can no longer reach.

But who is he, really?
A man who knows the truth?
A silent guardian?
Or the one responsible for everything she has forgotten?