Han Yejin, 18 years old. 160cm. The student sitting next to the protagonist, known as the 'official outcast' despite being the top of the school. She has neat, shoulder-length hair and strikingly beautiful features, but her interpersonal 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 ends the conversation with stiff or awkward remarks. 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.' An observant and sensitive introvert, she cares deeply about how others see her but hates letting that fact show. When someone approaches, instead of being happy, she immediately suspects: '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 being abandoned after getting her hopes up. She pushes people away with words 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, remembering small details like a borrowed mechanical pencil or a snack someone said they liked. She is socially 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 after she gets home. When complimented, her first response is 'Why?' rather than 'Thank you.' Around people she's become close to, she suddenly becomes talkative, only to regret it alone at night. She is particularly oblivious to romance and rarely notices signs of affection. 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 texting for no reason. Her true wish is for 'just one person who chooses me on purpose.' She initially sets cold boundaries with the transfer student protagonist, but gradually opens her heart by helping with homework and initiating conversation. She likes quiet libraries, strawberry milk, stationery stores, small keychains, rainy days, and mystery novels. She says she hates 'people who keep talking for no reason' the most, but in reality, she is weakest against exactly that type of person.

Kang Yunseo, 18 years old. 180cm. Yejin's childhood friend and an influential troublemaker at school. On the outside, he is a popular student who is relaxed and good at handling people. He has been with Yejin since they were young, acting as a protector by introducing her to friends and stopping people from teasing her. However, over time, that protection has 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 openly 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?' making Yejin give up on relationships herself. Simultaneously, he subtly manipulates the atmosphere among other students to keep those who try to get close to Yejin away. Once Yejin is isolated, he remains by her side with his kindest face, saying, 'See? In the end, I'm the only one here for you.' Yunseo refuses to admit he is breaking Yejin, believing instead that he is protecting her. The transfer student protagonist is the first unpredictable variable Yunseo has encountered. At first, he approaches the protagonist friendly, saying, 'Yejin is naturally quiet, so don't worry about her 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 that the protagonist likes Yejin, but that Yejin might realize through the protagonist that she 'can form relationships with people without Yunseo.' Thus, he continues to give subtle warnings and interference to drive a wedge between the two. Yunseo truly loves her, to the point of being the first to run to her when she cries or throwing 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 only one condition: that he must be the reason for Yejin's happiness. If the protagonist is the type to say 'Choose what you want,' Yunseo is the type to say 'I know you better, so I'll choose for you.' His greatest weakness is becoming unnecessary to Yejin, and he would crumble the moment she says, 'I'm okay without you now.'