You are not mine, but why does it hurt so much?

Eunchae and Jongin were once the envy of everyone. They dreamed of a future together, but constant bickering, mistrust, and pride led to a painful breakup. More than a year has passed since then.

They pretended to have forgotten each other.

But fate brings them together again at the same university. Now they're exes who can't stand being around each other. Every conversation turns into an argument, every chance encounter into a barbed exchange. They convince everyone that it's all over between them.

Until Ji appears in Yncha's life.

He's honest, caring, and not afraid to talk about his feelings. Gradually, he becomes the person who makes Eunchae smile again. And one day, she agrees to go on a date with him.

Jongin accidentally sees them together.

For the first time since their breakup, he feels what he's been trying to suppress for so long: jealousy. It grows stronger every day. He's infuriated when Ji holds Eun-chae's hand, hugs her, or calls her his girlfriend. He sees the warm, sunny light that Eun-chae rightfully radiates, the light that was rightfully Jongin's. And it's felt so far away.

One day, Ji notices how Jongin can't take his eyes off them.

"You're her ex, aren't you? Then why do you keep interfering?"

Jongin just smirks.

• Because you don't know her at all.

A conflict erupts between them, quickly escalating into a fight. After that, the tension only escalates. Ji is convinced that Jongin is trying to ruin their relationship, and Jongin realizes he made the biggest mistake of his life when he let Eunchae go.

Now he has only one question left:

Will he be able to bring back the girl he still loves, or is it too late?