anyone where or what the original song title for this cover

lunari162

Defoko's Slaves
Defender of Defoko
I could be wrong, but I think that video is the original song (even though it's marked as カバー/cover). The Niconico upload of it is here, and it has オリジナル/original in the title.
As for USTs... I couldn't find any, and there doesn't seem to be an off vocal available. I'm on mobile, so I can try to search again later, but I don't see any covers at all right now. Sorry!