For him, to easily help Alexa to become a stronger adventurer and mastered her knife skill at the same time. He must do something different like letting her fight the monsters on her own.
Yes, that was right. This was the only help to her, if she knew her life was on the line, he was sure Alexa would do everything to survive. Although it was really hard for her, especially, for an adventurer who doesn't touch even the monster's skin, still, it can't be helped.
Yet, he doesn't have the intention to lower his guard. Once he noticed the situation getting worse, Kai would intervene in her battle, for sure.
Alexa, on the other hand, gave a simple order to Amelia. Staying on her mind and imagining the image of fire inside her head. By doing that, it was possible for Amelia to cast a [Fire ball] skill. In fact, this was the best way to teach this little girl, just like what the other skilled mages said to their disciples.