I Don't Want To Marry A Succubus

In a world where supernatural beings existed and feudal superstitions ran rampant, The Great Elf Empire ruled the continent. 
Imperceptibly, they grew infatuated with power and wealth such that they failed to notice and regulate the spiraling upsurge of the rival Half-orc population. 
Due to the half-orc high fertility rate, their swelled numbers eventually triumphed over the elves despite their unrivalled skills. 
The elves retreated to a miniature continent having been driven out of their habitat. 
Doyle, a Trans migrator from the earth who happened to be the third Prince, is forced into a political marriage by the Emperor. 
To protect the Elf race and empire, he is required to marry a little princess from the devil clan so as to forge an unbreakable alliance. 
With the two races conjoined, they would stand a chance at defeating the Half-orcs. Prince Doyle is shrouded with doubt and unwillingness due to the buzzes and distressing rumors he heard about the devil clan’s maidens. 
Blindingly, he begrudgingly accepts the engagement unaware of the adventures and marvels he is yet to experience with the fabled succubus.