At least pay him for the paint he used! Paints are expensive, you know. And it's even more expensive for a street artist without a patron. Many street artists don't even have a proper room to sleep in.
The dude's right. From the very start it was clear he didn't think highly of her naivete and this was not a selection exam. This was a practical lesson. Dedicating your life fighting monsters isn't all fun and games. Drill sergeants in real armies would actually try to make you quit despite what...
Lily's reaction is probably the best thing about this manga. That's saying something after 21 chapters. Ai-chan would not complain if this manga is filled with Lily's shaky reactions.
Bitch! He helped you when he didn't have to, and you accuse him of trying to steal your dead brother's glory. Ai-chan is glad she left. Don't come back!