A/N : actually I don't really like detective story but yeah I try myself to make one. I’m not that smart so this is only my weird imagination so I don't guarantee anything. Please don't take it seriously. Just take it to entertaining yourself. Because my point is not the detective case but the romance between Myungyeol. But still hope you enjoy. Thank you. Love you all.

"Guys, I have a new case for you. This is about the serial killer in the girl school around Seoul. And this is the file that I got from the Seoul Police." Sunggyu said as he put the file on the table. Sungyeol took the file.

"The killer has unique way after killed the victim. The culprit would paint the wall 'Guest Who?' With pink lipstick and as the signature, the culprit would put a different number as code."

Sungyeol flipped through the file with the papers of evidence and gory photographs.

"So far, the murderer had killed 4 girl students. And most of them are the popular girl on their school and their school is the most favourite school in the area."

"First victim, Park Mi nah, 16 years old, a cheer leader from Seoungyang high school, Sungin-dong, was murdered on the toilet after class end and the murderer give number 2 as a code."

"Second victim, Bai Seo Yeong, 17 years old, school president from Nando High School, Myeon-dong, murdered in music room, the number code was 15."

Sungyeol kept looking at the file as he listened to Sunggyu.

"The third victim, Oh Mi Jun, 16 years old, a leader of music club from Geokdu High School, Seogyo-dong, murdered on the rooftop, and the code was 11."

"The forth victim, Kim Jan Di, 17 years old, a leader of baleria club from Mukdo High School, Muak-dong, murdered in the practise room and the code was 12."

"Strange. What code is that?" Woohyun asked curiously.

"I think maybe that's the sequence of the victim." Hoya spoke out.

"But the number was random." Sungjong commented.

"Maybe it's the number of the time?" Dongwoo said casually.

When the other was busy to crack the clue, Sungyeol his chin as he scanned the file seriously but remained silent.

"Ya, Sungyeol-ah, why are you so quite. Please help us." Woohyun groaned.

Sungyeol looked up. "I know where the next target."

"You do?" Sunggyu looked at him.

Sungyeol nodded. "Does anybody has a map?"

The rest of them instantly turned to him and gave him a weird look.

"Ya, Lee Sungyeol, we are solving case not going to learn geographic. Don't kidding us." Woohyun said annoyingly.

But Sungyeol just chuckled. "Just give me a map, Nam Woohyun-ssi. And I'll tell you the rest."

"I have a map on my office. Woohyun-ah, take the map from my office." Sunggyu ordered. Woohyun gave a 'damn-it-why-must-me' look but at the last he still go to take it. A moment later he came back with the map.

"Here it is." Woohyun put down the map.

"This is easy. Look, the first case happened in Sungin-dong. It's mean here." Sungyeol said as he circled the map. "The next second place is Myeon-dong. Here." he circled the next place. "The third place is Seogyo-dong. Here. And the last place is Muak-dong. Here."

"So, what do you think? Have you found out something, Yeol?" Sunggyu looked at him. Sungyeol looked up and smiled.

"If I'm not wrong, the next place would be Samcheong-dong."

"Why are you so sure?" Hoya asked.

"It's easy. The culprit tried to make a pattern after did the murder. And the code showed the alphabet of the next target. Look. If I draw a line from Sungin-dong to Myeon-dong then continue to Seogyo-dong and Muak-dong. Myeon-dong was across Muak-dong. It formed an A line. So it's mean the next place is Samcheong-dong."

"But isn't the nearest place from Muak-dong is Pireunde-ro?" Sungjong questioned.

"No, that's not the pattern. The pattern is S-M-M-S."

"How about Singyo-dong. I think it's nearer than Samcheong-dong." Woohyun asked as he pointed the map.

"I don't think so because Singyo-dong just a small district in town. So, I think Samcheong-dong is the main target." Sungyeol said confidently.

"And how about the code. Did it tell something?" Sunggyu asked again.

"The code refers to the victim. The first victim is Park Mi Nah, then the culprit wrote number 2. And then the next victim was found, Bai Seo Young, her name was started with B. The culprit then gave the code 15. And the next victim was Oh Mi Jun, and the last code that the culprit gave was 12. It’s mean the next target was the girl with the initial ‘L’.” Sungyeol concluded.

Sunggyu his chin, seem deeply thinking while the others tried to absord Sungyeol’s explanation.

“So, what we do now?”

“The most favourite school in Samcheong-dong is Woolim Girl High School.” Sunggyu started.

“Should we start our investigation from there?” Dongwoo asked. Sunggyu shooks his head. “I think it’s not enough if we just watch from outside. The culprit could be someone inside there. But I don’t want the investigation attract a lot attention coz this is too risky and we probably will lose the culprit. I want you to do the investigation secretly.”

“How?” Sungyeol raised his brow

Sunggyu smiled. “It’s easy, one of you just need to pretend to be a student.”

“What? That’s the girl school. We are men.” Hoya widened his eyes.

“Of course by dressing as a girl.” Sunggyu smiled or for exact smirk.

“What? I refuse. I can’t do that.” Woohyun raised his hands.

“Me too.” Dongwoo added.

“Don’t worry, that’s certainly not thw two of you. The candidates are Lee Sungyeol and Lee Sungjong.”

"Whaaatttt???” the Lee brothers yelled in union.

“Don’t think that you can ask me to do that just because I look like a girl. I don’t want to. Never.” Sungjong crossed his arms as he showed his diva look.

“And neither do I.” Sungyeol said nonchalantly.

“Calm down, Sungjong-ah. It’s not you.” Sunggyu smiled as Sungjong. Sungyeol immediately turned his gaze at the statement. “So, it’s mean MEE??” Sunggyu nodded.

“Ya, why me? Sungjong is more suitable dress like a girl. I’m too tall for a girl, and too manly.” Sungyeol said as he flipped his hair arrogantly.

“But Yeol, you’ve done it before. Remember, when we faced the ion case. You dressed as a hot y girl and even mesmerized Mr. Jun, the club owner.” Woohyun giggled which only get a dead glare from Sungyeol.

“But it doesn’t mean that you can ask me to do it again.” Sungyeol protested.

“Yeol, we count on you, you’re the smartest in the team so I trust you to do it.” Sunggyu said as he patted Sungyeol’s back.

“But why me?”

“If I were you, I would gladly take it. I have a good chance to see a fresh cute teenage girls and to be around them.” Hoya commented which got a hard poke from Sungjong on his head.

The rest of them just laughed silently. Sunggyu then turned back to Sungyeol. “Yeol, you’re not only help us here but also the rest of the innocent girl. Think about it.”

Sungyeol remained silent as he looked at them one by one then back to Sunggyu who gave him a meaningful look. Sungyeol groaned annoyingy. “Arasso, arasso, you don’t need to give me that look. I will do it.” The rest of the team smiled widely at the answer.