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I'm not really sure If I remember correctly but Daniel licks Litia's tears it gives him power or something and in exchange he gives her flowers..
Also the Crown Prince still ends up with the FL (forgot her name) and because Litia is helping him to woo the FL he gradually accepts her as his sister and became a bit of what you called a sis-con
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I also liked how the Crown Prince promise the right to success for the throne to Litia's child.. it's because CP is actually not the emperor's child but just the child of his lover.. the emperor loves his lover to the point he took the role of a father to the CP than our OG Litia.. like worst emperor/father ever.. lol
He neglects the OG Litia and didn't even know that OG Litia has a twin sister.. *drum rolls* MC from korea and OG Litia are twins..
They were experimented by the family side of their mother (can't remember the name) their mother protected the two of them as hard as she could but still failed.. the experiment affected MC more than OG Litia, resulting to the disease (forgot name) OG Litia then tried everything she could to transferred the soul of her twin sister to another world..
Sorry if I miss something but I don't remember it fully well

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I just wanted to say she ends up with Daniel but I feeeeeeeeel soooo baaad for those other MLs, I mean look how precious they are.
( ̄へ ̄)