Board Thread:Japanese VOCALOID discussion/@comment-34888404-20180526032838/@comment-53539-20180526105345

I think the page Kasane Teto answers most of these questions. I would pay attention to the "Team Twindrill" bit.

She is in project diva because CFM supports her and she is a guest, they also had Gumi in Project Mirai for the same reason.

Bare in mind, SEGA can use various Piapro assets for their collab games, thus this is why Neru and Haku are present in the games as well as some other rather out dated memes.