Ah, I don't know much of the details bc I haven't read the novel. But the ML did dance with another girl in front of everybody in both timelines, not bc he has feeling for that girl (for political movement).
In prev timeline, as far as I know, he didn't have a fix girl (aside for his sister), but he did neglected the FL, treat her badly, and disrespect her even though he (& his family) knew damn well FL is powerless and just a doll used by the Queen. They didn't give a single fuck.

Hey I saw that the ml cheats on the fl. Should I read or na, low-key don’t want to if the ml is just ass