Interesting. I like your little story. Be careful; some of your sentences were a bit awkward.

I myself would prefer if the Graum attacked first - or something to show he's not actually a peaceful creature.

Any chance you could elaborate on Yumi's name? If you made up the name to show that she's all cool and knowledgeable, maybe also show that physically; in her clothes, her odd jewelry, her hoard of magical books.

Anyway, great job. Keep writing!