This is a very typical fantasy-romance story.
But, that's not altogether a bad thing, of course.
Superior is a manga that takes all those romance cliches and plays it completely straight. Demon King (or, rather, Queen)? Check. Magnanimous hero who refuses to kill anyone except the Demon King? Check. And, now, all that's left is for them to fall in love!! Check.
Don't get me wrong. I personally really enjoyed Superior. It's a wonderful manga. The romance is really cliche at times, and the comedy falls flat more often than not... The characters are all likable and enjoyable enough, but after their initial appearances/arcs, most of them remain completely static. (Actually, I can't recall a single character developing as a character after their backstory, etc. was resolved.)
But, regardless, I like it.
Simply put, Superior is a manga with a lot of flaws, but it's not really a manga to be taken completely seriously or for the reader to be deeply invested. (The mangaka does try to make the drama compelling, and some of it is, but most of it isn't. Still, it's enjoyable enough.) As long as you are able to overlook these flaws and just take everything as they come, you'll probably enjoy Superior. It's certainly a wild ride, and I really did like it while it lasted.
Now, if you hate the romance/fantasy genre or can't stand cliches, this manga is obviously not for you. It's certainly enjoyable, but it really isn't one to change opinions. It's really more of a "guilty pleasure" than anything because, in terms of story or characters, it really falls flat. Where Superior truly shines is in its simple ability to make the audience enjoy the story, regardless of how ridiculous it is.