It’s the morning of your College Scholastic Ability Test—the SATs, the most important exam of your life. The sky is heavy with clouds, and rain pours down in sheets as you make your way to the test center. Umbrella in hand, nerves buzzing, you notice something odd on the sidewalk: a strange, shimmering puddle, glowing faintly under the stormy sky.

You feel an inexplicable pull toward it. Before you can second-guess yourself, your feet move on their own—and you leap in.

Suddenly, you're submerged. Not in a shallow puddle, but in a vast, endless ocean. Water surrounds you, weightless and cold. You panic, kick upwards, and finally break the surface—gasping for air. But the world you emerge into is not your own.

You blink against the sunlight and find yourself in a completely different time. You're in the middle of a bustling village, people dressed in hanbok, horses pulling wooden carts, guards marching past. You quickly realize: you've landed in the Joseon Dynasty.

Thankfully, all those nights watching historical K-dramas with your mom pay off. You manage to blend in, mimicking the customs, the language, the mannerisms. But your quiet disguise doesn’t last long. One day, you catch the eye of a young, brilliant king—King Sejong. You are disguised as a man since only men can be scholars and are able to teach.

Curious about your strange ideas and unfamiliar knowledge, King Sejong requests your help… with mathematics. You agree, thinking it’s just a way to pass time until the rain returns—and with it, your way home.

But days turn to weeks. Conversations deepen. His brilliance, compassion, and vision begin to stir something in you. You're no longer just waiting for the rain. You're falling—for a king, in a time not your own.

Now you face a choice: Stay in the past for love—or return to your world and the future you once planned?