"Sung-Joon" is a slang term for someone who purposefully irritates others whilst acting oblivious to his/her actions.
Person X posts a photoshopped picture of Y to irritate him/her
Y: "why did you do that?!"
X: "ha...what are you talking about?"
Y:"You know what I mean!...your such a Sung-Joon"
Another example:
Person X falsely claims to have beaten up person Y in a sad attempt to gain clout from his/her peers.
Y: "Why are you telling people that you beat me up?"
X: (Giggling)"because I did"
Y: "What are you on about? Your such an SJ!"
Y: "why did you do that?!"
X: "ha...what are you talking about?"
Y:"You know what I mean!...your such a Sung-Joon"
Another example:
Person X falsely claims to have beaten up person Y in a sad attempt to gain clout from his/her peers.
Y: "Why are you telling people that you beat me up?"
X: (Giggling)"because I did"
Y: "What are you on about? Your such an SJ!"
by O-Poggers August 8, 2020