Not that it took me a while or anything, but I finally got to seeing the Ultraman Moebius Side Story: Ghost Rebirth 1. (Not that the next volume isn't out in three days or anything... Must remember to order.)
I see why people said it's related to the movie. It is, somewhat. It picks up a side thread that I hadn't thought of before, but in retrospect could have wondered "gee, how did that...?" Style-wise there's a lot in common too -- kind of like a lite, episode 0 for the movie or something. The fight sequences in this DVD give a nice taste of what's to come in the movie. The director for this (Yokoyama Makoto) and the director for the movie (Sakamoto Kouichi) have both worked on the Power Ranger series, and likely have worked together. I'm pretty certain there was a lot of back and forth brainstorming between them on both works, since there are a lot of little points in common.
There's not a lot of story here, though there is a lot of "ooh, nice touch!" going on. Like the movie, I'm particularly impressed with the fight sequences not because they look cool (and they do), but because they're well thought-out. Continuing with the comparison, I'd say the fights in the movie look more impressive, and these look more like how people who've trained a long time to fight fight. Simple things like when fighting two on one the key is to line up the two on the same side, so they can't both attack at once.
There's a lot of small, subtle stuff going on that shows that it's done by people who watch the series -- and watch it over and over again. Little things that integrate I particularly like that Moebius will take cover. It's his style. He started out doing that waaaaaaay back in his first episode and it's nice to see it continuing. Monsters he's fought before show up, and he reacts in a way that you go "yeah, you know that attack, don't you?" Little things come up that make the alert viewer go "oh yeah, I remember that from..." It integrates nicely into the overall modern Ultra universe.
The music intrigues me. It's mostly themes from Moebius, only they're done in a different key from normal, or with the lead done on a differently-pitched instrument. Minor keys. Violas taking the part bold, brassy trumpets normally would. The tonal scale going down instead of up in a way that makes the music feel like it's upside down. To answer my own question from earlier, Voyager did a cover of the Moebius opening theme that was used as the end song for this OAV. It's... different from what I'm used to. Not bad, just, whoa, different.
So overall, I'm glad I waited until I wasn't falling asleep or in a rush to watch it. It's fun stuff, and for those who haven't seen the movie yet, it's a nice taste of what's to come.