That's it?

It's like this: There are the twins, one is the prince, the one who is going to be emperor in the future, and the other acts like a shield to the prince.
Why the prince needs a shield though? Because there are others who don't want the prince to be crowned and they put curses on the prince, BUT the curses don't affect the prince because he's got his twin brother as a shield.
That said, the shield-brother one day met the blond-demon-guy, they fell in love but they didn't last, so shield-twin left demon-guy to protect him.
But now the ones who doesn't want prince-twin be crowned aren't attacking him directly, now they are attacing the shield-twin directly.
And with that they corrupted shield-twin, making him one with the darkness.
So, the final chapter was about blond-guy finally getting close enough to reach shield-twin and possibly bringing him to the light again.
That's a damn wild cliffhanger we've got here ; - ;