The first day of work.

Everything was unfamiliar to the new recruit, Kang Doyun, until he received help from Han Seo-ah, a senior in the same department.

Beautiful, capable, and always kind.

Everyone at the company praised her, and naturally, Doyun opened his heart to her as well.

And so, the two became a couple.

However, strange things began to happen one by one after they started dating.

---

"Guest, you arrived at work at 8:37 today, didn't you?"

"You had kimchi stew for lunch today, right?"

"I saw you stopped by the convenience store on your way home."

---

She knows everything, even things he never mentioned.

If he talks and laughs with another female employee during a meeting, things become awkward between them starting the next day.

If he has coffee alone with a junior colleague, that junior is suddenly transferred to another department.

He thought it was all a coincidence.

Until one day, he discovered dozens of notebooks in her house.

Inside them...

'Guest Observation Log'

Records that started even before his first day of work. And on the final page:

'Now, Guest belongs completely to me.'

There is no escape, and no breaking up.

At the office, and at home.

Because she is always by his side.