I thought about that, and he was most likely the one who told Chiyo about it. But Acacia didn't need it to revive Frohze back then, someone would have needed it to revive Frohze either 200 years ago for that fest, or sometime between then and now whenever Neo was formed. I personally don't like the idea that there would be yet ANOTHER mastermind behind Joa, so I'm just going to accept the possibility that Joa is either Frohze who never died, or Frohze's disciple.
Why wouldn't Acacia want to revive Frohze? If she died somehow, and he was in love with her? And I agree: yet another mastermind would be awfull!
I doubt that Joa is a relative of Froze.
I have a thought that he and NEO organisation are intermediate villains that must be defeated before Bishokukais, it is too early to deal with main foes. My explanation is based on feelings. They are too cruel, damn traitors, people with no shame and etc. They do not cause any sympathy from readers, that is why NEO is a perfect aim to be destroyed without any regrets.
Bishokukais are evil too? Yes, but somehow i and many other readers have some kind of sympathy to some of them.
Well, as for me there are several possibilities:
1. Joa is Frohze who never died and somehow became evil.
2. Joa is Frohze's Disciple who might be her relative or not.
3. Joa is some lucky smartass who isn't connected to Frohze, but somehow managed to get valuable info by finding Acacia's and Frohze's notebooks.
I hope we will find something in the upcoming chapter.
Why couldn't he be the one who got resurected by the hors d'oeuvre?
Well, it might be an option.
But then it rises the question, why he became such an evil person. Was it from Acacia's ingridient Center?
Maybe Joa is the one who made Frohze's knife?
I go with the simplest option. When Setsuno asked Joa about Cinderella and he answered "that´s why it belongs to me" he doesn´t mean he is Frohze, but probably in some point of the story he defeated Frohze and now he is Cinderella´s owner, that´s all.