Ikusa Otome Suvia
Japanese title: 戦乙女スヴィア
Type: OVA
Source: Visual novel
Episodes: 4
Status: Finished Airing
Aired: Dec 22, 2007 to Aug 28, 2009
Duration: 27 min per ep
Rating: Rx - Hentai
Studios: Anime Antenna Iinkai
Producers: Pixy
Genres: Fantasy, Hentai

The King of Hell had held Odin, the ruler of Norse gods, captured in the Land of the Dead with the help of Loki, the Trickster. The Valkyries failed to save him and ended up becoming sex slaves to the demons. 

As a trade to free himself, Odin had the river source to the World Tree sealed, which will destroy the whole world. But before that, Loki had Freya, Chief of Valkyries, captured to counter Odin's plot. 

In order to prevent the World Tree to fall, Loki have to find 2 keys which are protected by 2 invincible Valkyries—Sigurd &amp; Suvia. And Loki turned his lustful attention on Suvia who was a Princess of Prishintia.

(Source: ANN)