Kaisa. Upon hearing that name again, the Ghost Lady's blade glows, making it clear that she understands it, that she remembers that name.
A cursed weapon should not have a soul as it has been consumed and corrupted to its creation. But the Ghost Lady seems to feel something beyond the sheer desire to destroy everything.
Another desire clings to her soul, causing fragments of her old life not to be consumed by madness. And the fact that she is not attacking Lucien and his wives is due to his pleasant energies within her.
"Kaisa?" Lucien speaks in a tender tone as he reaches out his hand toward the cursed sword. "Do you want to meet your sister again?"
Before Mira comments on how a cursed weapon couldn't understand and answer his question, the Ghost Lady, or rather Kaisa, flies towards Lucien and lands nicely in his open hand.
He smiles and holds the sword hilt gently. "Nice answer."