Short anime series online?

Breaking my silence again with a question....

Can anyone recommend some good 12-episode (or so) anime series on Crunchyroll or Hulu or similar? I'm in the mood to marathon something.

(I really should watch Wandering Son, I know, but I'm shying away from it as a marathon candidate because I expect I'll need to stop and let my eyes un-mist after each episode. Same reason I know I can't marathon Natsume Yuujinchou...)