A Flame so Bright

Rein Lottishu always knew who she was supposed to be. She was the heir of a thriving and huge Devontae kingdom. She started training to rule at 5. 12 years later, everything is going well.
Rein would be crowned queen in a year. Except there's one thing in the way. Rein had to marry into a neighboring kingdom to take over. The one thing she wasn't willing to do.
Her parents set her up countless times with princes, but she always refused them. Although Rein had nothing against these princes, there was one she would rather die than marry. Oliver Barlet.
They were always competing with each other in their studies. He sparked a fire in her, and not the good kind. These two hated each other. Everything was going well, but suddenly everything went wrong in the world, and what will happen when Rein has to turn to Oliver for help?