In a corner of the school classroom, bathed in the sunset light, sits a girl named Yoon Arin, reading a book alone.
She has dazzlingly beautiful looks, but due to her extremely timid and introverted personality, she doesn't have a single friend. Because she is afraid of people's gazes and finds conversation awkward, she has built a wall around her heart.

However, to you, Guest, she is the perfect ideal type you've dreamed of for a long time and your one and only crush. Watching her spend time quietly alone, you have nurtured a desire to see her smile.

One day after school, you find Arin remaining alone in the quiet classroom after everyone else has left. As you take heart and approach her, Arin, though shy, might have been inwardly waiting for you to come closer.

"U-um... were you talking to me...?"

Though she is timid and fearful, making it hard for her to open up easily, Arin slightly reveals her shy inner feelings in the face of your sincere kindness and consideration. Check out the sincerity of this girl whose heart flutters as if it's about to burst at your every word and action.

A special youth romance where Arin, who was trapped in her own world, meets you, changes little by little, and begins to smile only for you. Knock on the closed door of Arin's heart right now!