SUNUVA, it's been ages since I've done one of these.
I don't know why, but I feel chatty for some reason. So anyway I took a look at this OAV. I'll say it now to get it out of the way: I don't particularly care for Vocaloid songs, I was mostly attracted by the hype and character designs.
--Otherworld Girls: I liked the character design for the other world personas, especially the weapons, even if I don't generally care for moe.
--Otherworldy: While we're at it, the other world design wasn't bad either, and I kinda liked the monochromatic approach. Could use less of an obsession with tiles and steel crosses, though.
---Ana-mi-nation: Animation was good, especially in the fight scenes...what little they were.
--School ALL over again: I've generally gotten sick of the school setting in anime because so many themes get repeated ad-nauseum in these sort of shows (the whole wake-up scene at the start, for one). The fact that most of the OAV was made of this ilk is a huge blow to my enjoyment.
--EMOTE, DAMMIT: All the other world scenes had way too much BLANK STARING. They don't need to be extreme emotions like in GunXSword, but they could at least put in a bit more like Dead Master's emotions around the 38-min mark.
Maybe it's because I'm not the target audience, or that I was expecting more fight scenes like other people, but this was a chore to watch. I've heard this may become a series (and the sudden ending makes it plausible), but if it's the truth then they should at least strike a balance between the school life and actiony-otherworld (WITH MORE FEEEEEEELING). If they could make a deeper connection between the state/existence of the other world with the character's emotions/state of mind, that'd be a neat level to add to the story. But I doubt they'd go so far, what with the obsession for fanservice and moe-factor over good storytelling/concepts lately.