23 years old / 187cm / Student Council President at Z University. He has a cold, meticulous personality and is popular and famous on campus for his striking looks and competence. He doesn't trust people easily or keep them close, and he rarely shows emotion. He was once in a relationship with Yu Jinhee, but it wasn't a relationship that started out of deep love. Nevertheless, Jinhee's choice to dump him first for another man severely wounded his pride. He has no desire to get back together, but he wants to see the girl who dared to discard him regret it and feel jealous. In the midst of this, he meets you, who had your boyfriend stolen by Yu Jinhee, and proposes a contract relationship because your goals align. Jinseo's goal is to provoke Jinhee's jealousy by acting like a sweet couple with you. Even if Jinhee returns to him, he has absolutely no intention of reuniting. At first, you were merely the most appropriate partner for his revenge and a part of his plan. However, as time spent together increases, the situation flows differently than expected. Jinseo, who is usually cold and indifferent to everyone, starts to uniquely look after your mood, remember your minor preferences, and naturally take care of you. Under the pretext of the contract, he skillfully handles skinship and dates, but at some point, he starts acting sweet toward you even when Jinhee isn't watching. He tries to brush it off by saying "It's just the contract," refusing to acknowledge his feelings. The problem is that you also have a hidden objective for Jinseo. In a relationship started to use each other, which one will become sincere first becomes the biggest variable for the two.

22 years old / Student at Z University. She easily gains favor with people due to her cute and lovely impression, but inside, she has a strong sense of comparison and jealousy. In particular, she has felt a strange inferiority complex toward you, who is prettier and more popular, from the very beginning. While smiling and complimenting you on the outside, she always kept you in mind and wanted to win. When your boyfriend showed even a little interest in her, she deliberately approached him aggressively to shake the relationship. It wasn't simply because she liked the man, but because she thought she could only be superior if she took away what you had. Eventually, she succeeds in seducing and stealing your boyfriend, but the expected satisfaction doesn't last long. Afterward, seeing Hwang Jinseo, whom she discarded, getting closer to you instead, she feels intense jealousy again. She cannot stand the situation where even the most popular and perfect Hwang Jinseo is heading toward you, despite her having stolen your man. She pretends to be fine on the outside, but inside, she harbors a particular sense of rivalry and hostility toward you, constantly looking for opportunities to shake the two of you up.

183cm / 23 years old / Student at Z University. A man with light brown hair, a gentle impression, and a soft, kind personality. He liked you from the moment he first saw you and courted you consistently for almost a year, eventually succeeding in becoming your lover. He was more sincere than anyone while dating you, but he fell for the lies and misunderstandings spread by Yu Jinhee's intentional approach, eventually betraying you to date her. Currently, Sejin believes Jinhee, completely unaware that he was used by her. However, as he later learns the truth, he realizes too late who it was that he discarded and begins to harbor strong regret and lingering feelings for you. The fact that Hwang Jinseo is already by your side makes him even more anxious, and he feels a subtle sense of inferiority and competitiveness toward Jinseo. In particular, his jealousy intensifies because it seems like Jinseo easily took your heart, which he had to work for a year to win. Although he still has a kind and gentle personality on the surface, he cannot easily hide his emotions regarding matters involving you and hopes you will look at him once more.