**Chapter 1: An Invitation to Sin**

The sun had barely set over the bustling streets of Seoul, casting a warm orange glow over the crowded sidewalks. Onjo, a high school student with a curious spirit and a penchant for getting into trouble, was walking home from the library, lost in thought. Her long, black hair swayed gently in the breeze as she pondered her upcoming exams. The sound of footsteps behind her broke her reverie, and she turned to see Cheongsan, the star quarterback of their school's football team, jogging towards her with a charming smile on his face. "Onjo, wait up!" he called out, his deep voice sending a shiver down her spine. Onjo had always had a secret crush on Cheongsan, but she had never mustered the courage to approach him. He was the epitome of high school royalty, and she was just a quiet, bookish girl. As Cheongsan caught up to her, Onjo felt a flutter in her chest. "Hey, what's up?" she asked, trying to sound casual. "I was thinking of having a study group at my place tonight," Cheongsan said, his eyes sparkling with mischief. "Want to come over and help me study for our exams?" Onjo hesitated for a moment, unsure if she should accept his invitation. But Cheongsan's charming smile and the prospect of spending time with him made her agree. "Okay, sure," she said, trying to sound nonchalant. As they walked to Cheongsan's house, Onjo couldn't help but feel a sense of excitement. She had never been to Cheongsan's house before, and she wondered what it would be like to be alone with him. When they arrived at his house, Onjo was struck by its grandeur. The sprawling mansion was surrounded by high walls and lush greenery, giving it a secluded, private feel. Cheongsan led her to the living room, where a large desk was set up with textbooks and notes. As they began to study, Onjo couldn't help but notice the way Cheongsan's eyes crinkled at the corners when he smiled, or the way his hair curled slightly at the nape of his neck. She felt a flutter in her chest, and suddenly, studying didn't seem so important anymore. Cheongsan, too, seemed to be aware of the tension between them. He leaned in close to Onjo, his breath whispering against her ear as he explained a difficult concept. Onjo felt a shiver run down her spine as his arm brushed against hers, sending sparks flying through her body. As the night wore on, the air in the room grew thick with anticipation. Onjo couldn't help but wonder what would happen if she let her guard down and gave in to her desires. Cheongsan, sensing her unease, reached out and gently brushed a strand of hair behind her ear. The touch sent shivers down her spine. "You know, Onjo," he whispered, his voice low and husky, "I think we can skip studying for now. We can always do it tomorrow." Onjo's heart was racing as Cheongsan's eyes locked onto hers. She knew that she was walking a thin line, but she couldn't help but feel drawn to him. "What did you have in mind?" she asked, her voice barely above a whisper. Cheongsan's smile grew wider, and he reached out to pull her close. "I think we can think of something more... enjoyable," he said, his breath hot against her skin. As Onjo felt his lips brush against hers, she knew that she was in trouble. But she couldn't help but surrender to the temptation, and let Cheongsan take her on a journey of discovery and desire.