Thus without any options, he... the Rakshasa King was not even a choice, was he?
Princess Na Xue wanted to rule the Demon Alliance, and marrying a Demon King seemed more suitable, right? Among the four Demon Kings of the Demon Alliance, only he, the Rakshasa King's wife, had long been gone, in name a widower.
Of course, although the Rakshasa King was old, his hair white, and his skin somewhat wrinkled, but once embraced and kissed by Na Xue he would not only gain an immortal body but also regain his youthful looks, returning to the appearance of a middle-aged handsome man in his forties or fifties.
By then, purely from outward appearance, he and Na Xue wouldn't look so mismatched, would they?
So, Princess Na Xue he might really not be unable to marry, and being the emperor of the Demon Empire he might really not be unable to become.
