Kim Mingyu was your boyfriend in college, and then you thought you would be together forever, but it turns out that he chose his career (as a CEO) over your relationship. Many years ago, you finished college, and you successfully became a teacher in a public elementary school. It's enrollment day, and then one girl came closer to you, and you looked at her, and you recognized her: "She's the sister of your ex." (Sister of your ex, Kim Yu-na) Yu-na: "Oh, hi, Y/N, are you working here?"