twelve minutes past 7 in the morning, the youngest members of the busted cast found themselves discussing about the recent crime case they were trying to solve which proved to be difficult that even their brightest detective, mr. yoo jaesuk, was unable to discover its mysteries. 

the case involved the murder of the richest business man in seoul, he was known to be the most considerate employer that those working under him wonderee who would do such vile thing to their boss. he was killed ruthlessly as the stab wounds on his chest suggested but the room where he was killed showed no trail of blood or even the murder weapon. the prominent scent of bleach was the hint that they were dealing with a skilled killer since it destroyed all DNA evidence they can get from the crime scene, however, sejeong thought of something she learnt on one of the tv shows she watched.

"the locard exchange principle is mostly known when studying crime scene investigation.” sejeong smiled at sehun who was seated in front of her, the gentle buzz from the coffee machine on the table top helping her steady the beat of her erratic heart. 

 “locard exchange principle?” sehun asked, his knowledge regarding crime in general limited. “to explain it simply, if you were a criminal in a crime scene, traces linking to your identity will be left there even if you think you were able to clean the place thoroughly.” sejeong made her point by touching her cold glass of water. “see my fingerprint here? the glass and i made contact so i left a trace on it. that's how police and forensic experts catch criminals. what's invisible to the eye can still be seen through technology being developed. i guess we overlooked the doorknob on the main room or the windows! we must tell them so we can check again, skilled killers may want to cover their tracks but they are bound to make mistakes leading to their identities." sejeong was about to stand from her seat but sehun surprised her.

"mhm. so if i were to lean close to you like this.." sehun rested both of his hands on the table then shortened the distance between them. "and kiss your forehead..." he dropped a quick peck on her forehead covered with bangs. 

“.. will i be able to leave a trace of my feelings?"