TOH
Nagawa Mira is a huge issue. He has yet to hear the full details of how she got like this. But if she is able to use such a deadly poison without Lucifer being aware, then the threat to Sumire's life has increased. Why does the Nagawa family hate Sumire so much? From what he has learned from Lucifer, Sumire actually helped the Nagawa family out. She was the reason they escaped from debt and probably the reason why Nagawa Mira kept her seat in the Black alice council.
Lucifer admitted that he intended to get rid of the woman since she no longer had a purpose. How her families riches were the only thing he needed from her.
'But then I learned about her grandson being the guy lurking around my future wife.'
That woman needs a warning. She owes her current place to Sumire. She ought to be dammed grateful, not attacking her like this.