Kyousougiga is definitely a piece of work, but I might have to warn you that it may not seem to be very coherent at first. The ONAs definitely aren't very coherent, but having watched them a few times, I can say that the story means very little. This kind of thing does apply to a lot of slice-of-life, where the episodes stand alone and the anime is more centered around other elements.
You might be confused as to why I rate it so high. For an anime that wasn't meant to have a real coherent story at first, they did a good job at highlighting plot points. My first impression when watching this anime was "What am I watching and why is it so god damn awesome!?!?" The episodes, which are paced very quickly much like FLCL and the likes, do give you a sense of whats actually happening. Im trying not to spoil the plot points but by now most of you reading this have probably watched the TV series. Sparing some details, Young Koto is looking for her mother (also by the title "Koto"), who appears as a black rabbit hopping through gates to other worlds. Koto follows the rabbit, and ends up in the 13th parallel, a world drawn by a monk, where crazy, crazy shit happens.
The art is easily one of the most captivating parts of the series. Its colorful, with lots of fractals and great detail put into the animation sequences. Again, like FLCL, it seems they did a lot of experimental angles in their shots, and they worked magnificently. Imagine SHAFT without all the repetitive goddamn SHAFT-tilts. Every scene is fresh. The art also contributes to the sense of wonder that the anime conveys, enhancing its overall enjoyment.
The soundtrack is taylored to capture any moment just right. There are about 30 tracks in the OST, if that says anything about their reportoire of sound. Bear in mind this is for a series of ONAs that only spans about an hour in its entirety. Now honestly my favorite thing about the music is that it spans from acoustics and whistling to aggressive synths you would hear in hardcore EDM (electronic dance music, techno, whatever you wanna call it) and as a music producer, these make great samples. The easy-going sounds like "a whistle sounded" have a very nostalgic feel and sometimes I find myself whistling the tune when im unhappy.
Without going into analysis of all the characters, because that might count as a spoiler, I have to say that each character was designed very well, and their personalities are fun and interesting. As far as character design, Koto has many expressions about her and she wears them well.. The council of three are also well-designed. Yase is probably the most elaborate. Very much like a proper princess, and her outward appearance shows her as a child at heart. However, Yase is half-demon and will wreck shit if she doesn't get her tea. In a way she reminds me of a touhou character (not an actual one though). Kurama is very zen-like. He never gets angry and just lets life roll by him. Myoue is more human than monk, immersing himself in the pleasures of love, and all that. It might be confusing that he looks like the "original" Myoue, though. And lets not forget Mother Koto. She is insanely beautiful and emanates motherly love. Talking about Inari might spoil some of the plot, but I will say that my opinion of him changed, at least when the TV series aired because there was more continuation to the story which developed him into something else. But as far as the ONA goes, hes a loving father whose sole job is to raise Koto. A and Un, Koto's little lackeys, are like comedic relief. Last but not least is Shouko, an absurd gamer girl who has tonnes of gadgets and gizmos that control Mirror Kyoto. When I say "gamer girl" I dont mean the stereotypical girl who does things for attention, not that the stereotypes true. She is insanely dedicated to her job.
Kyousougiga 2012 was the first run of Kyousougiga that I've watched. That being said, it holds a spot in my heart. I was actually on a good dose of MDMA when i watched it the first time, but rewatching it still gives me that feeling of unconditional happiness. So if you don't do drugs then I guess Kyousougiga is one of the next best things.