I had forgotten all about this manga!
Then I remembered why.
There's more than one?
Great ones for example are "Kagerou Daze" and "Goodbye Declaration". Kagerou Daze is waaay more fleshed out with many songs so it clearly works better. But even Goodbye Declaration, which is one hugely popular song like here, managed to not ruin the premise by introducing original characters. It is translated up to chapter 9 and infinitely better.
We can't know just how involved the artists themselves really are but I think, when comparing "The Vampire" to "Goodbye Declaration", it is clear that one was more invested in pushing out a good product.
Little rant about this chapter and its implications
There are many manga based on (vocaloid-)songs. It is just as EchoGirl wrote, the adaptions that ain't one-shots can go anywhere since they only have that little bit of story to go off of. But that is the problem. They easily end up being incoherent story/writing-wise like here with original characters that just are not enjoyable.
Think about it. He is a stranger. What does him saving her all white knight add? What does the super close selfie add? He said he has no followers, why would she bother? (she 1minute before said "you must have many followers, let's exchange IDs") It all stops making sense right here.
Also, Jealousy can't happen yet. So he can't even be a tool. Why did the author have her enter the venue with MC to then just leave him alone all day? And even if it is MCs old band mate- why did she have to swoon for him this heavily? A compliment is okay. Thinking how handsome she find his face 2 times and then telling him face to face and spamming more compliments is a bit weird considering she was just with her crush (well, she did forget about him for most of the time in the venue it seems?)
I don't want to see the Miku-inspired Vamp-chan flirt up a stranger, after all day long running from MC which is the exact opposite of what this whole manga should be about (loved ch1 last panel), this is TOO MUCH artistic freedom.
I can imagine the ways this will be going after seeing that "5k follows for the photo with the hot guy!?". And it will most probably be even worse, sadly. Feels like this went past the target and is now some original Shoujo(+ possibly reverse Harem with the first dude that was teased)