Here's the revised version with improved grammar and writing style:
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Hours passed. Seongji Yuk sat in a chair behind the counter, watching something on his phone. Since it was nighttime, there were no customers. Suddenly, he heard a voice: "Senior, I heard you were recruiting a part-time worker?"
Seongji looked around but saw nothing. Startled, he paused. The voice spoke again: "Senior! I'm down here." Seongji stood up from his chair. In front of the counter stood a round, heavyset boy wearing glasses, a nervous expression on his face.
Seongji scratched his head, embarrassed. "Sorry, I didn't notice you earlier. Is your friend the one who came here a few hours ago?"
Daniel answered nervously, "It's okay, Senior. You don't have to apologize. Yes, my friend came here earlier."
Seongji nodded. "You don't have to call me senior all the time. My name is Seongji Yuk. What's yours?"
"I'm Daniel Park. I recently moved here."
"Oh! What a coincidence—I moved here a few months ago too." Seongji smiled. He could tell the boy was nervous and self-conscious, so he tried to act as friendly as possible. He asked Daniel some general questions—things one needed to know to work as a shopkeeper. Daniel was well-informed.
Since it was Daniel's first time at work, Seongji decided to stay with him and help out. After a while, his phone rang. He answered the call and went to the staff room to talk.
At that moment, three customers walked in. Though they had mature faces, Daniel recognized them as his classmates. The one in front said, "Four packs of Marlboro Lights."
Daniel stuttered, "I n-need to see some ID..."
The customer pulled out an obviously fake ID. Daniel said, "Um... I don't think this is your ID..."
The customer sneered. "Huh?! It's my ID. I just got fat!"
Daniel and the customer began bickering. Suddenly another customer entered—a kid with a pompadour hairstyle, pale skin, and two black "X" marks on his cheeks, wearing a white long-sleeved shirt with black stripes, black pants, and red sneakers.
Daniel recognized him as his classmate Zack Lee. Zack also recognized Daniel, but not as his classmate—as the random guy he'd had a scuffle with on the street the other day.
It seemed Zack was friends with the other customers. He said, "Hey, we don't need to go anywhere else. We can even grab some alcohol."
Hearing this, the group started picking up alcohol and cigarettes. After that, they put everything on the counter. Zack leaned toward Daniel. "Hey, let's make up for last time. Why don't you think of this as an apology...?"
Daniel didn't answer. Zack snapped, "What?! Did I say for fucking free?! What? You don't want to reconcile?"
Zack's friends started talking about the new transfer student at school—the one every girl had a crush on, including Zack's crush. Zack pulled at his hair in anger.
He released a sigh. "Haah... The truce is cancelled!" He threw a punch at Daniel's face. But the punch didn't land. Seongji caught it with his palm.
"Kid, you can't raise your hands against someone for no reason."
Zack looked at him with anger, but for some reason, he backed off. He left the convenience store with his group.
Seongji grabbed the alcohol and said to Daniel, "Help me put these back in place."
Daniel was a little surprised by everything. He stuttered, "W-what? Ah! Yes."
As they were putting things back, Seongji asked, "Did you know them?"
Daniel nodded. "Yeah. They're my friend's classmates."
Seongji said, "Hmm... Don't mind them. There are always people who like to bring others down. But what matters is staying true to yourself. Once you learn to do that, no one will be able to bring you down."
Daniel nodded slowly. Seongji smiled and ruffled his hair. "How about this? Let's call it a day. Let me walk you home."
Daniel immediately shook his head. "No, no. You don't have to, hyung-nim. I'll go by myself."
Seongji smiled. "Okay then. If you need help, you can always tell me. Fellow men should help each other."
---
After a while, Daniel reached his home. He took out his phone and called his mom.
"Oh my~~! Who's this? My son~"
"She's so glad..." Daniel thought as he smiled.
"Son, why aren't you in bed yet?" his mom asked.
"I was just taking a stroll. The wind here feels good~~"
His mom laughed. "Is that so? Your mom's also taking a stroll! So, son, how's your school going?"
"Don't worry, Mom. School was good. I also met a very nice senior today, so don't worry about me. How are you doing?"
"Don't worry, son. Your mom's doing well too. Am I sending you enough for your living expenses?"
"It's fine, Mom."
"All right, son. Don't worry about money or anything. Just study well, okay?"
"Hmm... I will, Mom. I'll head back after strolling for a while. I'll call you again."
"I love you, son."
Ending the call, Daniel's mom got up and started to pull a cart full of destroyed materials. In the darkness of the night, her back looked extremely lonely. But her face was filled with determination.
---
The next day
Vin Jin lay with his head down. It had been a few months since he'd transferred to J High. The kids here were wimps, so he didn't really like mixing with others.
"Hey, did you hear? The new transfer student from the fashion department beat Zack Lee!"
"Huh? What do you mean?! Wasn't Zack Lee an upcoming boxer in middle school? How could someone beat him?"
"It's true, it's true. The whole school is talking about it!"
The students were talking among themselves. The topic interested Vin Jin. He got up and yawned, then walked toward one of the students. "Hey friend, where's the fashion department?"
The students looked at him, shocked. Though Vin Jin was wearing a uniform, it couldn't hide his muscular body.
One of the students asked, "D-Do you want to meet the transfer student? Since it's lunch break, he should be in the canteen."
"Oh, is that so? Thanks, man!"
With that, Vin Jin left for the canteen.
Many students had gathered in the canteen.
"Hey, isn't that the architecture dept?"
"Yeah, it's Vasco and his group."
Students murmured. Daniel, who was eating lunch, suddenly greeted Vasco loudly. "Hi!!!"
Vasco glanced at the girl and student sitting beside Daniel. He misunderstood Daniel as a bully and approached him. It seemed they were about to have a confrontation.
Meanwhile, Vin Jin, who had just entered the canteen, was a little surprised. He took off his sunglasses and squinted. "It can't be, right? Is that Eli?"
He approached a guy with purple and pink mixed hair surrounded by girls. "Hey, are you Eli?"
Eli looked up, surprised. "Vin?! Why's he here?!"
Vin Jin said again, "Hey, Eli. Don't you recognize me?! Where have you been all this time?!"
Everyone focused their attention on them. Vasco, who had been leaving with his guys, also noticed.
Eli coughed. "Sorry. You might be mistaken."
But Vin Jin grabbed his shoulder. "The fuck?! Why are you lying?! I might always be wearing sunglasses, but I'm not blind, you fucker!"
Before Eli could reply, Vasco approached Vin Jin. "Hey... Who are you? Why are you messing with someone else?" As he said this, he grabbed Vin Jin's shoulder and started to squeeze it.
Vin Jin squinted. "Who the fuck are you, mustache? What's this supposed to mean?"
With that, he grabbed Vasco's shoulder and squeezed it. Vasco's face visibly contorted in pain, but he didn't back down. His shoulder started turning red, then purple.
Eli got up from his seat, and Jace also approached Vasco. Eli said, "Vin, leave him. Let's talk later."
Jace added, "Guys, there might be some misunderstanding."
Vin Jin released Vasco, and Vasco did the same. Vasco's shoulder was purple and throbbing with pain, while Vin Jin was perfectly fine.