
I don't think he was cruel as he was described as kind, I don't think there's anything showing he is anything negative. Its more of a mystery story tho, like why did he forget them when it was so obvious he tried to take good care of them before she was born, and also the mystery behind the aehri clan and her strange powers.
She's also clearly not trying to melt anyones heart, as she has scratched and has tried to escape from them many a times, its more like they're trying to appease a stray cat

psssh he forgot his cinnamon roll.... jk
I was exaggerating because thats just the trope, stern unapproachable father/king figures... and honestly we all know REAL royals are WAY too busy ruling to bother with their children
also... cinnamon rolls dont need to do ANYTHING to melt hearts... they just... exist. (she could literally claw their heart out and they'd still go "aww"... hence the cinnamon roll power)
I dunno what i was thinking was going to happen when this manwha has such a simple boring title. Like... I was thinking there'd be succession issues or some kinda royal drama.... nope, shoujo dad king and everyone is gonna treat her like a cinnamon roll ..bleh... I've seen it, done it... over it. lol
to be clear, the story isnt bad... just over done; you can probably find plenty of other stories with this similar premise... motherless daughter melts cruel king's heart with cinnamon roll powers... done.