Elf no Oshiego to Sensei
Japanese title: エルフの教え子と先生
Type: OVA
Episodes: 2
Source: Light novel
Genres: Fantasy, Hentai
Studios: Flavors Soft
Producers: Mary Jane
Duration: 17 min per ep
Rating: Rx - Hentai

Kobayashi Hiroki is a teacher for a tribe of elf students who came from another world. No one is sure why the world where the elves come from collides with our world. Hiroki however has fallen in love with Laranoa, one of the otherworldly students, which is strictly forbidden... So they act on their love in secret whenever they get a chance to be alone.

(Source: TMDB)