Harry turns, giving the duo a cursory glance. "Weapon. Guns. Ex-criminals. Interesting job occupation you have there, and I know quite a bit more about souls then you could ever dream."
He taps his forehead, a wide grin spreading on his face. "A certain Dark Lord, as our heroic friend," he paused for a moment, his eyes sparkling with... something, as he looked at the redheaded boy, "said, the third disciple of Heinrich Kremmlar, was in there. A piece of him. A piece of his soul. Mine, of course, assimilated and absorbed it - it overpowered it with purity and strength. His darkness was no match for my fire." He turns away from them, his wand turning and twisting in his fingers. He speaks as he looks towards the doorway, his tone mocking and cruel. "Oh? It's 'alright', because his soul will grow back? Tell me then, Weapons, what happens if you're scratched in your form? It tarnishes your body. It can be cleaned, restored, but you will always, always know that it was there. That is what she has done; she has torn away the essence of life for her family. Her defense is love, and her punishment is decided by the Council. After the War, naturally."
His head turns, and he winks at them. "After all, I'm only licensed to kill evil."
Shiki's eyes are a storm, whirling and breaking and neverending as Lelouch talks.
"...Heh. You think I care about any of that?"
He smiles, and almost looks normal for a moment, like he was just an average boy, instead of that dreadfully serious and scar-covered young man that was there seconds ago.
"You did it for her. You did everything for her. That's why I'll help you, even though you 'persuaded' me in a way that I don't really like. It's because you give a damn; and that's what really matters."