The male lead (ML) was bullied, and the only person who treated him kindly and acknowledged his existence was the heroine. Consequently, he fell in love with his idealized fantasy of her. Personally, I doubt it's love; rather, he seems obsessed with his own version of her. To me, it feels more like a horror story than a romance.
This "love" drives him to insane lengths to capture the heroine. His strategies and decisions solely revolve around possessing her, with a focus on self-satisfaction and zero consideration for how his actions might impact the poor girl and others.
He broke into her parents house to read all her social media posts and diary, multiple times;
He forced his former bully to set fire to a house so he could rescue the children (unforgivable) and became the hero;
He threaten heroine to kill her with a knife; menacingly threatening to crush her throat when she suggested a kind gesture (choking here)
The creators did an excellent job depicting a manipulative, Machiavellian criminal obsessed with the poor heroine, exploiting his role as a police officer in the name of justice (pun intended). The contrast between his facade as the good cop and his true nature is shocking.
The track where the heroine discovers his real identity and confronts him is truly frightening, with the voice actor's performance being amazing. The eerie laugh sends shivers down my spine!
The sound engineering elevates the scariness, especially when the ML suddenly gets close and speaks in your ears, saying, "I want to be one with you", the heroine's hasty retreat mirrors my reaction...
In a bonus track, he sets her free, thankfully.