Hitoriga The Animation
Japanese title: 独蛾 THE ANIMATION
Type: OVA
Episodes: 4
Source: Manga
Genres: Hentai
Studios: Office Take Off, Cafe de Jeilhouse
Producers: Pink Pineapple
Duration: 28 min per ep
Rating: Rx - Hentai

On the train to school one day, Shirakawa Sumire is molested. However, when she confides in teacher Takahashi, the nightmare escalates...

(Source: AniDB)