Congrats on your first post!
That could be possible, and I thought of that when I heard of the Sun Rune, but the Queen has it, and it has pretty destructive powers. I don't know if that's going to be the case with this rune. It may be the Rune of Dawn, or maybe even dusk. At this point, we just don't know. But also remember, even though in the real world, everything has an antithesis, it's not always that way in the Suikoden world. So, there may never be a rune like that.
"And as for the the end of the World, you need not worry. No one should worry about such a thing right now..."
-Leknaat, Suikoden IV