Nobody talks about this one. Each episode is a quiet character study disguised as a throwaway spinoff, built around the idea that the cruelest people in Kotoura's life were just broken themselves. By the time you understand why someone hurt her, you're not angry anymore, you're just sad for everyone involved.
The Troubled Life of Miss Kotoura: Haruka no Heya is a six-episode comedy ONA released in 2012 as a companion to Kotoura-san. Each of these short episodes presents one of the series' characters in turn, so the set works as a quick introduction to the cast of the main show.