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*SPOILERS* (what I read from other comments)
The ML is Emel, Estelle's first bodyguard. He left the FL without saying goodbye because he wanted to get married to her so he needed to gain an equal standing. But instead, the dude got engaged to the princess Iris (who is jealous of the FL), kissed the princess in front of the FL, apparently GOT MARRIED to the princess??! So really a full circle douche eh. He did all these things for the sake of exposing the royal family, but still, unforgivable!
Also I think in the end Emel and Estelle still end up together, so I'm dropping this one HARD.
I read until chapter 40 something, and I was still confused about who the ML is, so I read some spoilers...In conclusion I'm dropping this ╮( ̄▽ ̄)╭