>>10545497That completely slipped my mind for some reason. Let's try to deduce what it might be then.
Not a costume, she already said that.
Not Kuro Live2D, she all but confirmed that is never coming recently.
Not a new Original Song, she has had one before.
Not a Sololive, she has had one before.
As for voice acting in a game, she did Rakugaki Kingdom, Azure Lane and World of Warships as FBK… but thay is her playing herself so maybe it doesn't count. Could be her playing an original character (although she did so that Eroge pre FBK).
Anime voice acting is in a similar position, she played herself twice (The Detective is already dead recently and something small a year ago, forgot the name).
I honestly don't know what else it could be then, either she will escape the "I haven't done it before" condition on a technicality (e.g. Sololive with a much larger audience than last time) or she isn't being humble and it's really something that's not quite as big a deal as we thought.