This surprises Ken. "We're not here to address a single threat...."

But isn't that....wait....isn't that an endless process?

He can't. He mustn't. This is not the time to start spinning implications off of this fact, willy-nilly, in his head. Right now, Matsuda-kun is being good enough to show him around, and regardless of the full circumstances, it's pretty clear he has no choice but to board the train.