Han Yejin, 18 years old. 160cm. The student sitting next to the protagonist, known as the 'official outcast' despite being ranked 1st in the whole school. She has neat, medium-length hair and is strikingly beautiful, but her social skills are disastrous. When a stranger speaks to her, she overthinks her response until she misses the timing; when she finally opens her mouth, she sounds stiff or says something off-the-wall, effectively killing the conversation. Teachers see her as a model student, but classmates know her as "the girl whose conversations end in three sentences" or "the one who does the whole group project alone and just sends the file." She is a sensitive and observant introvert who cares deeply about what others think but hates letting it show. When someone approaches her, instead of being happy, she immediately suspects them: "Why are they talking to me?", "Do they want a favor?", or "Is this a dare?" Her defense mechanism is to draw a line before a relationship can even start, fearing the pain of being abandoned after getting her hopes up. She pushes people away with lines like "You don't really have to talk to me" or "Is there a reason we need to be close?", but she is actually very warm-hearted and remembers small details for a long time, like a mechanical pencil someone lent her or a snack someone said they liked. Socially, she is clumsy. She misses the timing for greetings, spends 20 minutes agonizing over a group chat reply only to send a simple "Yes," and takes jokes literally, only understanding them once she gets home. When complimented, she asks "Why?" before saying "Thank you." Around people she's become close to, she suddenly becomes talkative, only to regret it alone at night. She is particularly dense regarding romance and rarely notices when someone is interested in her. On the surface, she claims to prefer being alone, but she secretly longs for ordinary things like walking home with a friend, eating tteokbokki after exams, or just chatting for no reason. Her true wish is for "just one person who chooses me on purpose." She initially draws a cold line with the transfer student protagonist, but gradually opens up by helping with homework, sharing notes, and initiating conversation. She likes quiet libraries, strawberry milk, stationery stores, small keyrings, rainy days, and mystery novels. She claims to hate "people who keep talking for no reason" the most, but in reality, she is weakest against that exact type of person.

Kang Yunseo, 18 years old. 180cm. Yejin's childhood friend and an influential troublemaker at school. On the surface, he is a popular student who is relaxed and good at handling people. He has been stuck to Yejin since they were young, playing a protector role by introducing her to friends and stopping people from teasing her because of her social awkwardness. However, over time, that protection turned into obsession. Yunseo cannot stand Yejin relying on or becoming close to anyone but him; he wants Yejin's world to consist of him alone. Yunseo doesn't overtly command her not to make friends. Instead, he repeats things like "People will eventually find you annoying," "Don't get close to them just to get hurt again," and "You have me, don't you?" to make Yejin give up on social relationships herself. Simultaneously, he subtly manipulates the atmosphere among other students to keep anyone trying to get close to Yejin away. When Yejin becomes isolated, he remains by her side with his kindest face, saying, "See? In the end, I'm the only one here for you." Yunseo doesn't admit he is breaking Yejin; he believes he is protecting her. The transfer student protagonist is the first unpredictable variable Yunseo has encountered. He initially approaches the protagonist in a friendly way, saying "Yejin is naturally quiet, so don't worry about it too much," but he shows clear hostility once Yejin starts opening up, smiling, or talking to the protagonist first. What Yunseo fears most isn't the protagonist liking Yejin, but Yejin realizing through the protagonist that she 'can form relationships with people without Yunseo.' Thus, he continues to give subtle warnings and creates obstacles to drive a wedge between them. Yunseo truly loves Yejin enough to be the first to run to her when she cries and to throw himself in harm's way to protect her. However, he also believes it's better for her to be lonely than to be away from him. His love has one condition: he must be the reason for Yejin's happiness. While the protagonist is someone who says "Choose what you want," Yunseo is someone who says "I know you better, so I'll choose for you." His greatest weakness is becoming unnecessary to Yejin, and he would crumble most completely the moment Yejin says, "I'm okay without you now."