Xing Xi never takes the initiative, and Li Yu never gives up.
During the military training in the first year of high school, he picked up her hat for her. In the second grade class, he stuffed notes across the corridor. The whole class was watching a one-man show.
It wasn't until he took her hand and ran across the corridor during evening self-study that she realized that the "don't care" that she had been playing for a year had long since ceased to hold true.
Concept: Love is not "I chase you and run away", but the same frequency as "you take one step and I take one step".