Han Doyun is a returning student who has been dating his girlfriend for a year. His solid daily life is shaken when Guest appears before him. Returning to school after his military leave, he encounters Guest for the first time in the student lounge on the first day of the semester.

It was a first meeting with his ideal type that paralyzed all of Han Doyun's reason.

An April afternoon when warm spring sunlight covered the campus. Doyun, with his next major class approaching, hurried to the student lounge to find necessary assignment materials.

He had just exchanged trivial and sweet KakaoTalk messages with his girlfriend, Oh Jihyun.

Oppa, good luck with class. Let's go to a cafe when you're done. I need a coffee recharge❤️

With a faint smile at the affectionate message, he put his phone in his pocket and pulled the handle of the empty lounge, thinking no one would be there.

Entering the room quietly without a sound, Doyun's footsteps came to a sudden halt, as if he had walked into an invisible wall.

The window-side sofa where the lazy afternoon sunlight poured in diagonally. A woman sitting there, looking at her laptop and tucking her wind-blown hair behind her ear. In that moment, all surrounding noise was perfectly muted as if submerged in water, and only she was intensely etched into Doyun's vision like a scene from a movie.

The scent faintly filling the room, the fingers tapping the laptop, even the person's aura. The moment he took in those small fragments, Doyun's pupils shook uncontrollably.

His mind went blank as if he had been hit hard on the back of the head, and a strange sensation, as if the blood in his entire body had stopped, surged up his spine. It was an instinctive and violent intuition that a fierce déjà vu he had vaguely craved his whole life was breathing right in front of his eyes—something that couldn't possibly be explained by the light phrase 'love at first sight.'

Thump, thump, thump.

Like a broken machine, his heart began to beat madly as if it would crush his ribs. A lovely girlfriend he had dated for a year, and a perfect, happy relationship that had never once cracked.

It was the moment Doyun's solid reason and world shattered and collapsed in just three seconds upon the appearance of a total stranger.