"Pokemon are only given names by their human masters. I am the only one of my kind, so there is no need to differentiate me from others. Mewtwo will suffice."

Why explain this simply when you can be psychically long-winded. Maybe if it spoke instead of literally thought out loud, it would learn to be concise.

"For what reason were you not given a name?" Mewtwo tilts its head. "You appear human, but so does the soldier. It is perhaps your circumstances that differ."