On So What there is a red moon or whatever that is , they are all dressed in red. in Olivia Hye's solo ; egoistic , there is jinsoul's rap that says :

• "Hey, for the sin of swallowing you

You get bigger and bigger, beautiful you You are me, now I’m you Little by little, soaked into my veins On&on, you and me the endless cycle We can’t be separated, When I miss you I close my eyes and go to you for a while Close your eyes and you come closer to me"

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• now what I personally think it is, is that jinsoul is connected to kim lip and so does olivia , swallowing the red moon and sin means maybe she betrayed her and she shouldve never done that now it could be she betrayed her for olivia or idk for some reason.
• it could also be that the monster of so what possessed her when she wanted to destroy him he got into her and now he is in her?? " you are me , now i'm you " or maybe jinsoul IS the monster..? i dont know.