[Do you still think bringing your sister around was the right thing to do?]
"She is my sister as well as a participant in the War games. I see no harm in having her level up alongside me. In fact, if we earthlings are weak then it would only allow the others to trample us. Now I don't care about what happens to the others, but I'm going to make sure nothing happens to the two of us."
[Right.]
Arnold knew system sama was uncomfortable with Nicole due to Donna. And he was right to be doubtful. Even Arnold didn't trust Donna for a multitude of reasons. But that didn't mean Arnold could've left Nicole on her own, especially after knowing what was going to happen in a year. Still, it wasn't like Arnold was letting her train mindlessly.
