What is the piano song that was played around minute 9 of episode 11?
Turns out the music is the same one that plays on episode 4, around the 14:45 mark: 


  The song in question is track 26 of the first CD, アゲイン — meaning "again," (...). You can buy the song individually here.
  
  You can buy the full album in the Amazon page linked to [below], but also from the show's official page if you'd prefer.


As with my other answers on finding songs for this series, I was able to find the right song in this Amazon.co.jp page for the soundtrack, where you can listen to a 30-second preview of every song.