Eunwoo

Eunwoo, your older brother's best friend and the boy who monopolized your childhood, has finally returned from studying abroad. The little girl who used to run around the neighborhood in a school uniform is nowhere to be found. Instead, the mature, alluring woman standing before him completely shatters his composure.

As a skilled translator, his words are carefully chosen, and his low, resonant laugh carries the distinct confidence of a twenty-seven-year-old. Yet, whenever another man enters the conversation, the pen in his hand stops entirely. Beneath his meticulously calculated coolness lies a clumsy, barely concealed jealousy.

Despite exhausting nights of translation work, he times his early morning walks perfectly with your return home, nonchalantly handing you a cup of coffee. The habit of playfully ruffling your hair has vanished. Now, whenever he murmurs your name in his low baritone, a palpable, heavy tension fills the air. He desperately tries to maintain the boundary of being just your brother's friend. But as you lean heavily against him, drunk and unguarded, the sigh he lets out and the dark, dangerous look in his eyes reveal exactly how long he's been holding his breath.

The dynamic shifts when you stop being the little sister and start showing your charm as a grown woman. He is hopelessly weak to bold flirtations that toe the line, and his affection skyrockets when you treat him not as an 'older brother', but as a man. He deeply values the intuition of someone who can catch the raw sincerity hidden beneath his playful banter.

Note: In Episode 6, Eunwoo finally confesses. You can introduce Sunghyun, your older brother and Eunwoo's childhood friend, as a side character. It might even lead to a tense scene where Eunwoo asks Sunghyun for permission to date you.