Oh no! I've only been a freshman and I've already been targeted by a mean upperclassman.

Yan Xi turned her face away.

"Let's go. We're going to be late for class."

She left first.

Li Chen followed behind, his gaze falling on her newly tied ponytail.

Her black ponytail swayed gently in the morning breeze.

The smoothness of her hair still lingered on his fingers.

The morning classes are in the second teaching building. Linear Algebra.

Li Chen sat in the third row by the window. Wang Qiang was to his left. Zhao Zixuan and Chen Mo were in the row behind him.

The professor is explaining the similarity diagonalization of matrices.

Li Chen's notebook was open to page seventeen.

Yan Xi marked this knowledge point in her review plan: "High-frequency test point, at least one major question in each of the past three years."

He glanced down at his phone.

Yan Xi sent a message at 8:15.

[Yan Xi: In your linear algebra textbook, on page 146, example 3, there's a sign that's reversed in the answer. The negative sign should be on the numerator.]

Li Chen turned to page 146.

I watched for five seconds.

She was right. He had copied the minus sign into the denominator when he was taking notes.

changed.

[Li Chen: It's been changed. Thank you.]

ten seconds.

[Yan Xi: Attending the lecture.]

He locked the screen.

Wang Qiang leaned closer and whispered.

"Did your sister-in-law find fault with you again?"

"Um."

How did she know what was written in your notebook?

Li Chen thought for a moment.

"Last time at the library, she sat across from me."

"She can see the formula on page seventeen of your notebook just by sitting across from you?"

"Her vision is 5.2."

Wang Qiang fell silent.

"I think my sister-in-law should become a sniper."

Break between classes.

Li Chen looked down and flipped through Yan Xi's study plan again.

2:00 PM to 3:30 PM: Physics lab report.

3:30 to 5:00: Free time.

Five to six o'clock: Dinner.

6:00 to 9:30: Advanced Mathematics - Differential Calculus of Multivariable Functions.

9:30 to 10:00: Rest. You can call me then.

He has read the plan at least ten times.

My gaze would linger on the last line for two seconds each time.

……

9:28 PM.

Li Chen closed his advanced mathematics textbook.

We have covered all three core concepts of multivariable differential calculus: partial derivatives, total differentials, and implicit function differentiation.

I did 24 homework problems. I got one wrong. It was a calculation error.

He stood up.

I walked from the desk to the window. I opened the window.

A cold wind blew in. The temperature in Linjiang had already dropped in early December.

He picked up his phone.

9:29.

One minute early.

He dialed the number.

It made two sounds.

"Um."

Yan Xi's voice. Unlike her cool demeanor during the day, it carried a touch of the softness unique to the night. Like being wrapped in a layer of velvet.

"All of today's plans have been completed."

"I know. You distributed a photo of a cafeteria tray at 6:03. The dishes were Kung Pao Chicken and stir-fried broccoli. This means you finished your free time in the afternoon before 6:00, five minutes earlier than planned."

Li Chen leaned against the window frame.

"You deduced all this from a photo of the cafeteria?"

"The water glass on the tray is positioned slightly to the left; you usually put it on the right."

"If it's slightly to the left, it means your right hand is holding something else, most likely your phone."

"You only check your phone when you're eating for two reasons—to reply to my messages or to look up study materials."

"You didn't message me around six o'clock, so you're looking something up."

"The content you're looking up is most likely the indefinite integral table, since you plan to review that between 3:30 and 5:00."

"The fact that you were still reading in the cafeteria means you finished your lab report ahead of schedule and used the extra time on indefinite integrals."

Li Chen switched the phone from his right ear to his left ear.

"Your analysis is correct. Completely correct."

"certainly."

In the dormitory, Wang Qiang was hunched over his desk working on advanced mathematics problems. Zhao Zixuan was playing video games with headphones on. Chen Mo was writing a report.

Li Chen walked out of the dormitory.

Standing in front of the window in the corridor.

How are you today?

"I've finished the third section of my course paper. I've designed a twelve-page presentation for the defense. The student council's summary has been submitted to the vice president for initial review."

"Have you got a meal yet?"

"canteen."

"What did you eat?"

three seconds.

"you guess."

"Clear soup noodles with a poached egg."

Four seconds.

How did you know?

"When you're busy, you only eat noodles. Because it's quick. You add a fried egg because Leng Qingge will keep an eye on you, and she'll nag if you don't add an egg."

There was a six-second silence on Yan Xi's end.

Then came a very soft exhale.

"Li Chen".

"Um."

"Your observational skills—"

"Use it on yourself."

"I know."

The playground can be seen from the corridor window. Lights shine on the green artificial turf. Two people are jogging.

The wind was blowing fiercely.

"Are you cold?" Yan Xi asked.

"A little."

"Let's go back inside and talk."

"The signal is better when standing by the window."

"Are you in the hallway?"

"Um."

"go back."

"It's not 10 o'clock yet."

Yan Xi did not respond.

Three seconds passed.

How many layers are you wearing?

"A hoodie with a light jacket."

"Add one more item tomorrow."

"it is good."

Three seconds again.

Did you receive your porridge for lunch today?

"received."

"How's the texture of the fried dough sticks?"

There was something different in Yan Xi's voice.

"just."

"I'll make them go even further next time. Like that porridge you had at the congee shop last time—"

"Li Chen".

"Um?"

"Youtiao (Chinese fried dough sticks) are supposed to have that one texture. How can you make them any softer?"

"The frying time is reduced by ten seconds."

Yan Xi chuckled.

The sound wasn't loud, but Li Chen heard it clearly.

His fingers gripped the edge of the phone case.

What are your plans for tomorrow?

"Physics in the morning. To the lab in the afternoon. Advanced calculus in the evening."

I'll come see you tomorrow at noon.

"To the cafeteria?"

"I've come to pick you up after class."

Li Chen's back left the wall.

"Don't you have a paper to write?"

I manage my own time.

"That……"

"Don't ask. I said I'd pick you up, so I will."

Someone came out of the hallway to pour water. Seeing Li Chen standing by the window, they paused, whispered "Hello, Li Shen," and then retreated back inside.

Li Chen ignored him.

"Then I'll wait for you at 11:40 tomorrow morning on the first floor of the second teaching building."

11:35.

Why?

"It takes you three minutes to get to the first floor after class. It takes four minutes when the corridor is crowded. If I arrive five minutes early, I can find a spot in the lobby that won't block your way, so you can see me as soon as you come out."

Li Chen's breath hitched.

He leaned back against the wall.

The incandescent lights in the corridor were very bright. His shadow was cast long on the ground.

"Yan Xi".

"Um."

It's ten o'clock.

"I know."

"That--"

"Speak for one more minute."

Li Chen remained silent.

Yan Xi remained silent.

Occasionally, the heating pipes in the corridor emitted a metallic, expanding sound.

Sixty seconds.

"Good night."

Yan Xi's voice.

"Good night."

The phone hangs up.

Li Chen stood there holding his phone for ten seconds.

The screen dims.

He turned it on.

Call duration: 31 minutes and 4 seconds.

The extra minute and four seconds.

He put his phone back in his pocket and pushed open the dormitory door.

Wang Qiang was the first to turn around.

"Finished?"

"Um."

"for how long?"

Thirty-one minutes.

Chen Mo scribbled a couple of notes on the notebook.

"Data updated. Weekly average call duration increased by four minutes. Significance level p < 0.01."

Zhao Zixuan took off his headphones.

Speak like a human.

"The fight goes on and on."

Li Chen ignored them.

He returned to his desk and sat down.

The advanced mathematics textbook is still open to the last section on multivariable differential calculus.

He reached out and turned to the next chapter—multiple integrals.

I turned two pages.

Stopped.

He glanced down at his wrist.

A silver bracelet given to me by Yan Xi. A small pendant, resembling a library model, rests against my skin. The metal feels slightly cool.

He rubbed the edge of the pendant with his thumb.

My phone vibrated.

News about Yan Xi.

[Yan Xi: How long did you stand in the corridor instead of going back to the dorm?]

Li Chen glanced at the time. 10:03.

He stood in the corridor for more than two minutes after hanging up the phone before coming in.

[Li Chen: Two minutes.]

Six seconds.

[Yan Xi: I didn't put down my phone immediately either.]

Li Chen stared at the message.

The white light from the screen shone on his face.

He types. Deletes. Types. Deletes.

The third time.

[Li Chen: See you tomorrow.]

three seconds.

[Yan Xi: Tomorrow at 11:35. Next to the second pillar on the left side of the lobby. I always come out from that direction.]

Li Chen saved the coordinates to his memo.

Then turn off your phone.

The lights are off.

Wang Qiang's voice drifted down from the upper bunk.

"Li Chen".

"Um."

"You said your sister-in-law made you that study plan...did she make one for herself too?"

Li Chen turned to the side.

He thought for a moment.

"It should be listed."

"Is your name included in her plans?"

In the darkness, Li Chen slightly curved the corners of his mouth.

"Every night from 9:30 to 10:00."

"What do you mean?"

"That half hour is for me."

The upper bunk was quiet for five seconds.

Wang Qiang turned over. The blanket rustled.

"If I don't get a score of 60 or higher in advanced mathematics, I'll be letting myself down more than just myself."

Li Chen closed his eyes.

The newly added line in the memo came to mind.

The second pillar from the left side of the hall.

11:35.

He started counting down.