Shaft is on a bit of a roll with regards to music in their two prominent animes this past 8 months, Bakemonogatari and Arakawa Under the Bridge. I seriously love Meg Rock and they did a great job on Bakemono, now Arakawa came out of the gate running with a seriously great OP and ED from Etsuko Yakushimaru and Suneohair, respectively.
I never could say I was a fan of indie rock bands, but there's something subconsciously appealing to me in these Japanese songs. Sadly, the full versions of Arakawa's OP and ED songs aren't available, yet. The OP Single will be out on May 26th and the ED single will be out June 23rd. In the mean time, here's the OP and ED if you have yet to hear them: