It was toward the end of 2012 to beginning of 2013. Mark and Vill were dating, but they hadn't come out yet while Kim was dating Jett. Mark and Kim were filming a lakorn together and sparks flew, so they began texting flirty messages to each other like the most famous one is Kim to Mark saying, "I miss you so much, I think I'm going crazy." Something like that. Everyone uses LINE. That LINE convo was leaked. Mark and Kim said it was nothing, even Boy came out saying normal friends can LINE like that. All fingers pointed at Vill as the culprit who leaked it. Vill denied it saying why would she? There's nothing to gain from it. Mark and Kim fans were accusing Vill as the culprit saying she wanted to sabotage Mark and Kim by leaking the LINE. At this point Mark and Kim were pretty much teaming against Vill. Bottom line, Jett and Vill were cheated on by Mark and Kim but Instead of feeling sorry for these two, people took Mark and Kim's side because at that time, their koojin status was already established. Fans were actually in support of Kim breaking up with Jett, which eventually happened about a few months later and continue to bash on Vill.
Son has always been very open about his feelings for Vill. When they asked him about it, he said, he is concerned about her because he was the one who invited her to be in the ET industry together, so with Vill confronting such a huge scandal, he doesn't want people to think of her negatively because she's not like that. People close to her will know. He encouraged her to stay strong.
We're guessing, Son probably told Vill to stay away from Mark because Mark has always had a bad reputation as a wannabe player slash Casanova, but Vill didn't listen, opposed Son, and got her heart broken. Son probably got his heart broken by her too at that time according to some Son fans who have followed him since the beginning. Ever since then, Son and Vill try their hardest to avoid each other in person and in words.
