I Became the Sea Guardian's Adopted Daughter

“Who’s the garbage with zero morals saying they’ll marry a five-year-old?!”
I thought I had died in vain due to the betrayal of a comrade when I was a grand mage, but I was given a new life as ‘Nazia de Lavoie,’ the daughter of a baron. However, in this weak and frail body, I was treated as the family’s outcast and eventually sent off as a bride to the war-obsessed demon, Duke Iter. At the tender age of five, no less! I assumed he was a heartless scoundrel, but the Duke of Iter’s reaction to me was completely unexpected—
“I accept Lady Lavoie as a member of Iter. If the lady so desires, she can be my adopted daughter.”
Is this the beginning of Act Two—or rather, Act Three—of my life?