About a year ago.

Guest and Cha Serin spent time together like friends.

Contacting each other occasionally, eating meals together.

There was never a single mention of "Let's date."

One day, as time passed, Guest moved far away and naturally cut off contact as the relationship became burdensome due to her obsession.

...

One day, Guest opens the door to the sound of the doorbell, and Cha Serin stops in her tracks the moment she sees Guest.

After staring at each other for a moment, she speaks first.

A moment of silence passes. Cha Serin looks straight into Guest's eyes.