Well! Names, I think of those on the spot as well, or just get a random name generator.

As for plot.... Well it could be a kingdom that tries to appease the "demon lord" who had used to reside there long before their ancestors, so then the demon king could be unconsciously watching the younger prince as he does his daily things around the castle with his older twin sister. (She leaves since she was found appealing to someone far away, and has to travel, so she doesn't turn up often, just the beginning. The point is, when the two are together, thy make a very sadistic duo, torturing people who have disliked them before. But once the old sister leaves, the man doesn't know what to do with himself, and becomes somewhat depressed, pushing away those women who tried to flirt with him.

That's it for now, but it does change as it goes on, I like keeping it dynamic and unknown. But that's the plan~ or so... ^^