This is every Northern Cold Duke meets Warm (?pale?) Tropical Clumsy Beauty who opens his heart trope rolled into a hamster wheel and shot out of a bazooka.
Theo is actually the dumbest, most one-dimensional character ever written, and he's written poorly. Of course his mother is dead. Of course he's a fearsome warrior. Of course he's just the most intellectually compromised loser with no actual work to do running his duchy.
Yuna is ??? Inexplicable? She has no skills or purpose, other than of course being a prophesized saintess! Otherwise she's clumsy, ignorant, naive, and pretending to be in love when she supposedly came into this marriage for transactional purposes. And why is she a tropical tribal seafaring princess who is ghostly pale and owns exclusively European clothing?
The writing is so bad in this, it's almost entertaining to read for how bad it is. It isn't helped by the fact that the art is inconsistent, laughably scaled (Yuna is that hamster meme eating a banana when she stands next to Theo), he is approximately 4 miles wide, his head is tiny, her breasts are the width of her entire shoulders, his hands! His yaoi hands. Every now and then I'll be charmed by a drawing of one of them, and the next frame they look like that drawing sent through a black hole and spaghettified.
Unless you have nothing else to do and are looking for a quick snort to waste a few minutes between feeding yourself and relieving yourself, do yourself the favor and skip this. I read a few chapters, chuckled, and flushed the toilet.