Reasons

"Is this where it is?" 

"It is thick."

"Can you cut it?" 

Aerton's group managed to reach the four ice walls that Leysha left behind. Of course, it took them a while since they had to kill the remaining demons standing in their way. 

Aerton couldn't help but realize that the enemies were so strong that Anna had to go all out. 

"I think it's better if we call Captain Howard here and let him make a decision. Even if we help Miss Anna, we won't be strong enough to fend off the enemy's attack. We might even become a burden to her." Aerton shook his head and ordered, "The rest of you will maintain the position and inform Grandel to take the command. I'll inform Captain Howard."

"Yes, Sir!"

Aerton hurriedly crossed the river since the problem was truly beyond his ability.

…

In the meantime, Anna and Leysha were staring at each other.