Diarmuid might not be able to tell exactly that the smile is fake, but he can sure tell it's not completely 'right' either. The boy frowns for a moment before stomping his foot slightly, "Be friends!" The words are stubborn, but also frustrated. It's that reminder again of what it is like when the man who says he is his father but isn't is there, upsetting everyone and how there is nothing he can do to fix how upset people are then either.

"I want to learn some more. Someone come teach me something," the boy looks at both Lelouch and Suzaku before walking back over to where he had been practicing and waiting for someone to follow. Learning and practicing what he has learned makes Diarmuid happy so maybe it will make them happy too where talking hasn't.