What is the song (piano) that was played around the ninth minute 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.