Original: 비밀 사이
Trapped in an escalating love square, a salaryman must navigate his tumultuous feelings for a colleague, a former tutor, and an heir.
Daon is a rational and calm person in his company and known for often fighting with his colleague Sunghyeon. One day Daon once again sees Jaemin, the senior he admired in university, along with Suhyeon, the heir to the company, and a relationship emerges between the four…
When Daon becomes distracted at work, Sunghyeon proactively notices and starts caring for him. Their relationship starts to become more and more ambiguous.
Suhyeon returns to the company as a department head and asks Daon if he’s still in contact with Jaemin. Jaemin confesses his attraction to Daon, and the entanglement escalates.
A secret contract is revealed, and Daon is forced to come to terms with past relationships along with new department challenges. After a drunken party, Daon calls a certain man.
After the drunken night, Sunghyeon gives Daon the cold shoulder, leaving him feeling confused As Daon tries to remember what happened last night, Sunghyeon reminds him they kissed. Meanwhile, his relationship with Jaemin and Suhyeon becomes more tense....
When Suhyeon starts interfering with Daon’s work and emotions, Sunghyeon gets triggered and a fight breaks out in the workplace. Meanwhile, Suhyeon reveals that Daon’s sad past may be connected to Jaemin.
After learning about Jaemin’s past actions, Daon decides to take a stand and tell Sunghyeon how he feels. At the same time, the company is rocked by a scandal, and Daon leaves his job. Just as he tries to get his life together, he gets kidnapped.
Sunghyeon realizes that Daon is missing and tracks him down to where he is held. During the confrontation, Sunghyeon gets injured while trying to protect Daon. While at the hospital, the two finally confess their feelings to each other.
