The kind of mystery that this human is isn't quite the kind that would make Mewtwo want to hold onto his name for deeper investigation, but...it's appreciated anyways. A little bit. It's a thing for humans, right. Mewtwo will remember it.

It looks at Souji and gives him a long nod, closing its eyes, to show it heard him.

As they start up the tunnel, Mewtwo keeps pace with Souji, neither trying to take the lead nor trying to give the human the lead. It becomes tense again as soon as the Heart room is out of sight, glancing back and forth constantly, and to Souji more than once to see how he's reacting to the situation.