Only the author can give the truest answer why Saehyun kidnapped and assaulted Sumin (hell, someone should ask her that in that question site). One way of looking at it, would be Saehyun did it out of vengeance since he figured Sumin is the reason why his younger sister is left in a miserable state - something that pissed him off (it's clear in the side-story he has some brotherly affection for Seju). Another way would be that he did it to save both Seju and Sumin in a twisted kind of way, perhaps figuring Seju can't go on living without Sumin at the time and would wither herself to death, and Sumin in turn would feel mighty guilty for Seju's death and head down a self-destructive path.
Regardless, don't see how that justifies Sumin to keep coming back and torment Seju for ten long years. Like FFS, Seju wasn't even the one who kidnapped and assaulted her. It was her older brother, so why not take your anger and revenge out on him instead? Since she already decided to break up with Seju because of the cheating beforehand, she should have done just that a long time ago and moved on without having anything more to do with her ex's life....
last edited at Feb 24, 2020 5:57PM