It's an anime by Gainax and Madhouse that's a ton of reality-warping fun until the show turns a bit more serious and then eventually does a Gainax Ending. At least it's a happy one, though.
Arumi and Sasshi are twelve-year-olds in the Abeno region of Osaka. They live in the Abenobashi shopping arcade, but unfortunately the economy isn't what it was and the shops are moving out. Arumi's family are moving to Hokkaido. The real world in this show isn't a particularly warm or comfortable place. (There really is an Abeno-ku in Osaka, by the way, and its redevelopment has caused many older commercial districts to be demolished or gutted.)
Fortunately, though, Arumi and Sasshi won't be spending long in reality! From ep.2 onwards, they're dimension-hopping. Most of the show's episodes are high-energy comedic genre parodies and deconstructions, including:
2. Fantasy RPGs, especially Dragon Quest.
3. SF, including 2001, Star Wars and various giant robot anime.
4. Hong Kong cinema, including comment on rip-off business practices, Jackie Chan movies, hopping vampires, etc.
6. 1930s gangster flicks and Film Noir.
...and more. My favourite was ep.8 and its skewering of Visual Novels, since I recently watched Clannad and as a result bought Kanon and Air. Look at the art style shift! Look at the character designs! The show points out the ridiculousness of the storytelling formula, as Sasshi has the time of his life and Arumi loses all patience in a big way. If you're a girl being forced to live in a harem universe, expect to be frustrated. It's at once hysterically funny, saying things that needed saying and even managing to bring in unexpected character sincerity and story developments.
The show's first half (roughly) is just fun. The animation is wild, the music is funky (especially the jazz) and the jokes made me laugh. It's highly entertaining. There's also a recurring character called Mune-Mune (i.e. "Breasts-Breasts") who lives down to her name in a series of outrageous outfits.
The show then changes direction. We return to reality to see some backstory that turns joke characters into real people with their own private tragedies. One of these is Mune-Mune. Sasshi and Arumi work out what's going on and how it links with onmyouji and the 11th century. It turns out that someone's going to die. The show becomes an exploration of reality vs. escapism. Should you accept the real world and live in it, or should you go on hiding away in all your favourite fantasies with the help of magic and self-delusion? This seems to be going one way, but then the Gainax Ending comes along and yanks you in another. You also don't get much time to process this, by the way, since it's a short scene just before the credits.
(A Gainax Ending, incidentally, is a finale that doesn't make sense, is heavily symbolic and/or will leave you wondering what the hell it all meant. This can be seen in different forms in Gainax shows like Neon Genesis Evangelion, Mahoromatic, GunBuster (maybe), He Is My Master, Kare Kano, Panty & Stocking with Garterbelt and of course this show. That said, though, this is a more audience-friendly example than, say, Evangelion, since at least it's fairly clear what happened. The explanations are straightforward, once you've accepted the dimension-hopping, 11th century reality-bending mysticism, reincarnation and time travel. What might throw you is Gainax's willingness to omit large chunks of what you'd expect from a season finale and of course the final volte-face. I admire Gainax, but I have to admit that there's a reason the Gainax Ending doesn't get done very much. Traditional finales are probably more satisfying for a general audience, both emotionally and intellectually, although that's not to say that Gainax Endings can't blow your mind too.)
I like the main characters. Twelve is young enough to be clearly a child, but also old enough to be genre savvy, cynical when required and very funny. Both children can get on the wrong side of a world and spend an entire episode suffering for the sake of comedy. Sasshi is an idiot. Arumi's smarter than him, but unfortunately shackled to Sasshi as far as sorting out the dimension-hopping is concerned. They're close friends and there would surely have been romance had these events taken place when they were eight or ten years older.
Lots of Osaka dialect, though. Rich, juicy Osaka dialect.
Would I recommend this show? Sort of. It could be argued to go downhill, with the first half being lighter, funnier and more entertaining than the second. Admittedly that's because the second half grows a plot, themes and serious stuff, but even then the Gainax Ending will probably put people off a bit. However it's still explosively imaginative and energetic, with lots of charm and some truly inspired bits.