Heart Stain

"Let's date until we graduate." U-Hyeon has a secret crush on his homeroom teacher. His best friend, Do-Ha, finds out and confesses his feelings for him. But then he makes an interesting proposition: "Go out with me. Fall for me before graduation, and I win. If you don't, you win." Can U-Hyeon like someone other than his teacher? (Source: Manta, edited) Note: Includes six extra chapters.