Do you think Killing Stalking is a Stokholm Syndrome Story

Yes, it is.
Yoon has BPD, Borderline Personality Disorder, and so he's a bit...different.
Borderline personality disorder (BPD) is a serious mental illness that centers on the inability to manage emotions effectively. The disorder occurs in the context of relationships: sometimes all relationships are affected, sometimes only one. It usually begins during adolescence or early adulthood.
To be in love with someone who abuses you and even threatens to kill you is probably a clear sign of Stockholm's Syndrome. Seeing as most people would just grow to resent someone...