Just my thoughts in the comment. I've already had thoughts about this but with the latest update it feels more concrete, but I think the radical anti-noble faction killed Lapis's noble half sister and Lapis is Aurora. After the death of her sister, the family forced Aurora to become Lapis in her stead. In Chapter 10, Lapis says "My entire existence is just an act" and it truly is. In Chapter 1 page 28, in the story of the game, when Lapis and Diana are fighting she says, "That thing died a long time ago" signifying that she hates herself and has been been feeling guilty about the real Lapis's death. At the end of Chapter 4, Lapis says, "I am Lapis Tenebrae" to remind herself her role and her plan to get revenge. I don't know how the revenge plays out but with Vino's ability to read minds and how disturbed he is with Lapis's plan, it tells me that it is dark, deep, and extremely calculative to the point he wouldnt want to be on the bad side of Lapis. In the game, Vino sided with Diana possibly in hopes to save Lapis in his own way. And the reason why Lapis is so surprised about Natori's "foreseeing" power and wanted Natori to become hers is because it can be seen as being one step closer to her dead sister.
