Fantasy romance with children (as main lead or otherwise)

I entered a novel in which the heroine who reincarnated as a saintess has to walk on a thorny path.
'Yeah, nope!'
I, who decided to walk on a flower path, abandoned the original frustrating family
and adopted my bias as my dad in our first meeting.
"You, be my daddy!"
The story's final boss and villain!
But now he's just my dad. Fufu.
"Daddy, why is your name also daddy? So cute."
"What did you eat for breakfast? Handsomeness?"
As I dream of a happy ending for Daddy, there's just one more huge

Fl is the child

A princess, neglected by her father, the emperor, decides to take the throne after his sudden death. But when he unexpectedly returns alive, their already strained relationship turns into a battle of wits and wills