"So if Taekwoon didn't kill Jaehwan, then who did?" Sanghyuk asked.

"That's the big question now, isn't it?" Yoohyeon asked, not taking her eyes off the broken chain that lay on the ground by Taekwoon's knees. 

"If we need to look into it some more, let's do that," Sanghyuk suggested.

"Y-yeah, just a minute," Yoohyeon held up a hand.

Sanghyuk paused leaning over to see what she was staring at. When he found the shattered chain on the ground, his lips pulled into a smile.

"What just happened?" she asked.

"You broke one of his chains," Sanghyuk explained.

She turned to him, fear and confusion in her eyes. "Please explain to me what the hell is going on."

He sighed deeply. "The reason we approached you, was so that you could help set us free, right?" She nodded. "Well, this is part of it." 

He gestured to Taekwoon. "Those chains that bind him can only be broken by uncovering the truth. You proved that Taekwoon was innocent, so that broke the first chain."

"What do I need to do to break the others?" she stammered lightly.

"Find the truth," Sanghyuk said. "The more you find, the chains will break. You break all the chains, you set all of us free." 

She weakly nodded. "Let's do this."

"Alright, so how do you find the real culprit?" Siyeon asked.

"Not from this bit of info," Yoohyeon said, walking up to her with a pile of files and papers in her hand. "Which is why I'm going to start from the beginning. Family histories, anything that can be of help."

"It would be helpful if any of their classmates were around," Siyeon suggested, raising an eyebrow at the massive amount of files.

"I checked that too," Yoohyeon said. "Of the classmates I could find, they're either dead or pursued careers abroad, so there's no chance of contacting them. Taekwoon was an only child. Jaehwan had an older brother, but he died of an autoimmune disease."

Siyeon sifted through the papers to find exactly what Yoohyeon was talking about. "This is cool," she mused at her friend's ability to dig up stuff. "So what have you found out?"

"Well," Yoohyeon shrugged. "It's not much, but it's a start. Lee Jaehwan was the heir to this really rich and influential real estate company, and Taekwoon was the heir to this pharmaceutical company," she related. "They went to the same school, this prestigious school for basically rich kids."

"And...?" Siyeon prompted. 

"They were rivals," Yoohyeon said. "Taekwoon was a bit emotionally...off from the start, but he studied well, and always topped the school. Jaehwan moved in his second year of high school, immediately took his place at the top. It made sense that they'd compete, and quite ferociously." 

"But why would Taekwoon kill him then?" Siyeon asked.

"That's the thing, he didn't," Yoohyeon said. "Which is why we need to find out. Any theories?"

Siyeon shrugged. "Another classmate maybe? Someone with sociopathic tendencies?" she suggested. "Does it have to be a classmate?"

"The kill was a sloppy job, and the autopsy suggested signs of a struggle," Yoohyeon informed. "It obviously wasn't someone who knew what they were doing, rather, it looks like they got in a fight and then someone gutted him."

Siyeon sighed, looking over the vast majority of files they needed to go through. "You know what would be easier? If any of those guys' siblings were around."

"I told you," Yoohyeon replied, not taking her eyes off the files, "Taekwoon was an only child and Jaehwan's older brother was sick from an autoimmune disease-"

"No, I meant their friends," Siyeon corrected.

Yoohyeon lifted her eyes from the files and stared at her friend. "What?"

"They obviously had friends, didn't they?" Siyeon clarified. "You told me about them, they kept trying to prove Taekwoon's innocence but passed early. It would be nice if any of them had a sibling who was there when the whole thing happened."

Yoohyeon scoffed. "Are you serious, Siyeon?" she asked. "There's no one alive! They're all only children. Even if they had siblings, they obviously didn't survive past 60."

As she talked, she looked back down on the files, which just so happened to be the registry of Hakyeon, Wonshik and Hongbin on this particular page. Their families were small and simple, only children, parents deceased, no known uncles or aunts, no siblings...

Wait...

Her gaze lingered on the family registry of Hongbin, and she scanned the list again. 

Alright, parents, deceased.

Lee Hongbin, deceased.

Lee Y-who was that? 

Lee Yoobin? 

Born 1958?

Alive?

Yoohyeon raised her head, open slightly in wonder. Siyeon narrowed her eyebrows when she saw her friend's state.

"Uh, Yoohyeon, are you-?"

"Siyeon, you're a genius!" Yoohyeon exclaimed, scaring the hell out of Siyeon who jerked back hearing her loud voice.

"Yoohyeon, what happened?" 

Yoohyeon's face broke into the widest smile she'd seen. "How on earth did you know?" she asked. "Lee Yoobin is Lee Hongbin's younger sister, and she's still alive!"