Sang-hyun and Su-ji, who once shared a sweet romance, broke up. A year later, they end up in the same class and are paired together for a writing project on the theme of love. They decide to write about their own past relationship, and as they work on the book, they realize that what they once dismissed as simple emotional conflicts were actually deep differences in values. Through the process, they finally open up about the feelings they couldn’t express back then.