It started a bit slow but then the story really got punchy near the end and really sucked me in. I really liked the decision presented to the sister, especially after talking to the dragon more. I also like that you can sort of figure out what the spell was from the spell name.
The art is great with the distinct style and colour palette that is consistent throughout. The writing was really good, I really felt like they were siblings (and the older brother, infuriating like one lol). It was impressive how you gave the characters depth very quickly so that there was some deliberation on the choice you get to make.
Awesome stuff!