Seiko Oomori is awesome, and definitely worth an obsession!
And speaking of going around the bend, I think I've found my new favorite more-underground-than-underground idol group: 小牧戦国少女隊 (Komaki Sengoku Shōjo-tai). They seem to be the official idol group of the city of Komaki (a suburb of Nagoya), which means, I gather, that they're a Rec Department thing (which means in turn that they perform at street fairs, weekend art shows, and neighborhood swap meets or whatever). But they're actually remarkably good for a small-city Rec Department group, and I like their material.
Or maybe I finally have gone insane. Here's their Xmas gig, at some kind of small-scale parking-lot festival -- there's at least one other clip of them performing in parking spaces 56 and 57, so I guess that spot is kind of home turf for them...
If madness made us strong, we would all be invincible.