Volt: This is pretty clear-cut backstory. The guy giving him his electrical powers, in case you missed it, is Doctor. Afterwards, Volt goes insane... I almost feel sorry for him, amidst my laughter. When he first attacked the guy, I laughed my arse off.
Linx: What kind of place is close to Tokyo and allows you to hunt deer with a gun? Not many places, I think... Anyway, I liked this video, seems to go pretty well with the song. However, unlike Volt's video, I've no idea what Linx's past is like. There are four characters in this -- Linx, white-haired guy (not Volt?), brown-haired kid and AYA. I assume that two of them in this list are the same character...
For what it's worth, I see the famous OIOI department store (pronunciation: Marui) in the background, which suggests Shinjuku or Shibuya to me, although there are other areas it could be. Feels like Shibuya, but Kokubunji is closer to mountains and forest...!
Garagara: This is probably the closest to a music video instead of hints of backstory. They even have an hourglass (see lyrics). The place Garagara is staying appears to be called "のぞみ園" or "Nozomien". Translates to something like "Hope Garden" and, while I have no justification for this, I think that sounds like an orphanage.
File is here