It was past two in the morning when Jae-hyun finally opened his laptop.

The house was quiet. Only the occasional sound of a car passing by outside could be heard, and the phone on his desk hadn't rung with any notifications for a while. He opened a new document and stared at the blank screen for a long time before typing a title.

[Causes of excessive interest in a specific individual.]

The cursor blinked beneath the title. Jae-hyun thought for a moment and then wrote down sentences one by one.

• Waiting for contact. • Excessively remembering trivial words and actions. • Feeling bad when seeing them with others. • Thinking of them even when not meeting.

His hand stopped after writing the last sentence.

It was no big deal. They had spent time together today as usual and parted as usual. The only thing that had changed was that the laughing face kept coming to mind on the way back.

Jae-hyun leaned back in his chair and closed his eyes.

He thought about what was so special about that smile. There was nothing special about it. It was a face he always saw, a voice he always heard. Yet, strangely, once it came to mind, it wouldn't easily go away.

He looked at the screen again.

[Possible Causes] • Dopamine secretion • Attachment formation • Psychological dependence due to familiarity • Activation of reward circuits by repeated positive stimuli

He stared at the last line for a long time before adding one more phrase.

• A trick of the hormones.

Jae-hyun's fingers stopped.

...I suppose so.

He muttered as if to himself and pressed enter. Emotions were ultimately like that. They only had grand names, but if you looked inside, they were just a series of minor physiological reactions. Love, jealousy, and longing were all nothing more than signals created by the brain.

It was simple when thought of that way. But suddenly, one strange point remained. Jae-hyun put his hands on the keyboard again. Then why this person, of all people? This time, it wasn't written easily. After moving the cursor several times, he eventually left one line as it was.

Why her, of all people.

He stared at the screen and then slowly picked up his phone. There were no new notifications.

After hesitating for a moment, Jae-hyun opened the messenger window. The last conversation they had was on the screen. It was a meaningless conversation. Nevertheless, his finger couldn't leave the screen for a while. Eventually, he typed briefly in the message input box.

What are you doing?

Jae-hyun stared at that sentence for a few seconds. Then he deleted it all as if nothing had happened. The cursor was still blinking on the laptop screen.