This is clearly destined for a het ending. When Diana starts slaughtering commoners, Lapis is gonna be like "oh damn, I don't even need to steal your jewel lets just team up and crush these people." Diana accepts, this shocks Natori out of her "I can fix her" trance and finally makes her wrestle with her moral conscience over serving a villain. She teams up with Gran instead who gives her a job she can be proud of without moral guilt. Lapis is shocked that the person she thought accepted her doesn't, and finds comfort in Diana's simpful arms, before they are both killed by Gran. Natori and Gran get together in the end.
0/10, terrible manga, Neko Tarou why would you betray me like this, remove the yuri tag
(this post is a joke please don't get mad at me)
Rubeus also dies because once he realizes Gran is terminally straight his depraved homosexual heart decides he'd rather kill him than see him with someone else