I thought this was technically the second half of Season 1, not Season 2?
Well, it's Book 2: Spirits
. It's true that the original 12-episode order was expanded to 26 episodes, encompassing Books 1 and 2, pretty early in the game; but I don't think the Book 2 episodes were shot as part of the same production season, since reportedly they're being done by a different animation studio, Pierrot in Japan, with oversight from Studio Mir, the South Korean house that did Book 1. (At present there are plans for four books/52 episodes.)