[ Rosaria mentioning that there's a slim chance those they've lost can come to life in this world through their Shards makes him think of the Shard in his possession. Even now, he doesn't know whether or not to believe that what he has is truly the physical manifestation of Diluc's soul, especially after what he'd learned about Heliopolis and their fake Shards, but— ]

... If there's a chance to bring them back, then I'd rather they're allowed to roam freely than be confined to a rock. At least they can decide for themselves then.

[ And making hard choices wouldn't fall on his or Rosaria's shoulders. It'll spare them the responsibility in case they wind up making the wrong choice.

The Diluc and Master Crepus of this memory remain unaware of his internal plight, and that's probably for the best. He'd rather remember them at their happiest rather than be plagued with thoughts of their disappointment in him, for giving up on the idea that it's possible to bring Teyvat back. ]

Whose soul did they leave in your hands?