I like the writing and the general story idea.
The 7 / 6 kingdoms thing is confusing and also how many kids go to the training camp,
I was counting characters all the time and thought about if it´s 6 or 7 kingdoms.
In some panels there are 6 kids in some are 7. I think it would be better to make this
clearer so readers don´t have to figure that out by themselves