Love Hina: Motoko no Sentaku, Koi ka Ken... "Naku na"
English name: Love Hina: Motoko's Choice Between Love or Swords: Don't cry!
Genres: Drama, Romance
Type: Special, Episodes: 1
Aired: Sep 27, 2000
Studio: Xebec
Source: Manga
Rating: PG-13 - Teens 13 or older
Synopsis:
Out of nowhere, Motokos' sister (Tsuroko) appears and is ready to pass on the dojo. However, Motoko is still not quite as strong as her sister and when her big sister finds out about this, she gives Motoko an ultimatum- Motoko must beat her sister or marry Keitaro!

(Source: Animelover27)