Onegai☆Teacher: Himitsu na Futari
English name: Please Teacher!: Secret Couple
Genres: Comedy, Romance, Sci-Fi, Ecchi
Type: OVA, Episodes: 1
Aired: Oct 25, 2002
Studio: Daume
Source: Original
Rating: R - 17+ (violence & profanity)
Synopsis:
Kei and Mizuho are having some marital difficulties, and Mizuho's family decides it's high time for a visit. 

(Source: ANN)