This is all a guess. I feel like the Grand Duke at first didn't like her, but later on when he got to know her, he fell in love with her. That's why he let her called him by his name months before she died. I'm also thinking that he did something for her to go back in time and he also went back. That's why it feels like he knows what she's thinking since she keeps feeling her "dream" is happening in real life.
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Yuriel is looking for her weakness and Yeldryia (mc) hinted that her weakness is Nadrica (the guy in the first chapter and the one that's only loyal to her). I just thought that was really cute and hope nothing happens to him or I'll fight someone. (๑•ㅂ•)و✧