Volcano is Vulcanus' Daughter and nothing more.
Flonne is a candidate for Vulcanus's old job.She's studying to be an Angel again; and we can see her Angel sprites in the promo art; so it's going to be part of the main plot. Flonne can at least pretend to be an Archangel as seen in Raspberyl Mode in Disgaea 3. Volcano is the other candidate.
Disgaea 4 will go Meta-recursive, and will make its serious moments an over the top parody of its own Sliding Scaleof Seriousnessversus SillinessThe second Promo suggests it. And the games into video has hints of it too.
The obligatory second mode will star FuukaThere's already at least one piece of art with her in the human world - in her "pre-Prinny" life. The second game mode, like the Axel mode, will be a prequel to the main story and cover Fuuka's descent into delinquency, but uniquely, will take place in an alternate modern day human world, filled with monsters and the like.
Desco and Asagi will team up.Asagi wants to star in her own game; Desco wants to become a final boss. Clearly a match made in the Netherworld, and they simply must join forces — all with the intent of eventually facing off in their very own spotlight title, of course...!
The Netherworld the game takes place in? Axel's home world!Disgaea 2: Dark Hero Days has the last chapter taken place in a children's orphanage where building contractors have been commissioned to build an Overlord's castle. Axel stops them, of course, but that doesn't mean the castle doesn't ever get built. Cue Time Skip, and Overlord's castle is finished, with the antagonist as the Overlord. That explains how the Dark Hero is without a cameraman or director in sight; he's home!
Valbatoze has a direct connection with this Netherworld's previous Overlord.In all three of the previous games, the main character had a direct connection with the previous overlord (for the first and third ones it was the main characters father and in the second it's their girlfriend) So going by this pattern, it seems almost obvious.
Valbatoze will be voiced by Yuri Lowenthal.He looks the part...
The names of angels are actually Nom de Guerre.It would explain why there are now two people named Vulcanus: the events of the first game led to the first becoming Unpersoned, and his Code Name and ranking were assigned to someone else. As for why Flonne got to keep her name after becoming a Fallen Angel, she never exactly disobeyed Lamington's orders...plus, the audience is too used to calling her Flonne by now.