I think when Seoin finds out that Jaewon bullied YW so badly, he might literally dig up his grave and burn his bones lollll. After that, he’ll probably confront his adoptive parents, especially his adoptive mother. And on the same day, he might also find out that YW never abandoned him and that he actually came back...but his mom gave him money and... Seoin would definitely give her absolute hell and cut all ties with her after that. That could be what pushes his mother to target YW, not wanting to lose her only remaining son which might then lead to YW’s condition in chapter 1.
I think when Seoin finds out that Jaewon bullied YW so badly, he might literally dig up his grave and burn his bones lollll. After that, he’ll probably confront his adoptive parents, especially his adoptive mother. And on the same day, he might also find out that YW never abandoned him and that he actually came back...but his mom gave him money and... Seoin would definitely give her absolute hell and cut all ties with her after that. That could be what pushes his mother to target YW, not wanting to lose her only remaining son which might then lead to YW’s condition in chapter 1.