プロジェクトセカイ 壊れたセカイと歌えないミク

Simbiat

I thought this was a stand-alone movie. Turns out it's related to a game and some other mini-series. And looks like you need to be familiar not only with Vocaloids, but also with the characters, because there are no introductions here. Thus you need to play the game, at least. And, yes, they use Vocaloids to voice the respective characters, too, which is definitely not for everyone.