On the second day, Asther didn’t go with Claire anymore. Instead, he went to train Octavia. And there is a good explanation for this.
At the moment, no matter what she does, Claire won’t be able to keep fighting for a solid ten minutes without getting drained. Gaining more stamina doesn’t happen that quickly.
That’s why he decided to let her continue the routine for five more days. This isn’t enough for a normal human. But Asther knows that Claire is far from normal as well. And he has high expectations for her. That is also why he knows that she won’t give up on the hellish training no matter what.
He already gave her the items that she needed. More stamina potions and a refill on a couple of water bottles from a nearby stream. Asther found the later mentioned location when he went to
