Love
Vash was amazed and overjoyed. Meryl was skeptical but eventually had to admit the truth. Milly just smiled and said she knew it would work all along.
She had healed Knives. Not completely— there were still open wounds on his soul that would only become scars in time. But the anger was nearly gone, and when he was with her, he seemed to smile more.
Milly had gotten them together. She'd watched and seen that each had a need the other could fill.
Who'd have ever thought that the heart of a madman could be healed by a stray kitten?