Rune of Assassin

A redhaired girl is lying on the ground, wounded. The world around her is being destroyed. Everything around her is exploding.
AKANE: So this is the cause of my actions? Did I train and fought all my life just for this?
She looks on her right. On the ground there's a glowing rock, radiating its magic. Tears start falling down her face.
AKANE: It's all my fault.
''AKANE'': Pathetic girl. All my life I was hiding my emotions... They taught me to do so. And now, tears. Ha! Pathetic. The whole universe will cease to exist because of me... Because of my emotions, because of them... Because of him. I'm no assassin. I'm weak. And just like that, I'll die.

You must be confused. Don't worry, I'll take you to the beginning, where it all started.