Natural: Another
English title: Teacher's Pet
Japanese title: ナチュラル Another
Alternative titles: Teacher's Pet (2)
Type: OVA
Source: Visual novel
Episodes: 2
Status: Finished Airing
Aired: Feb 25, 2000 to Jun 25, 2000
Duration: 27 min per ep
Rating: Rx - Hentai
Studios: Arms, Triple X
Producers: Green Bunny
Licensors: Kitty Media
Genres: Hentai

The story is about a young girl who falls in love with her teacher who was formally her sister's boyfriend. Although tension builds as he falls for another another female teacher and rumors of him and the student. 

(Source: ANN)