Based on the game by Lune.

This is an alternate retelling of Ride of the Valkyrie.

After being captured by the demon king's army, Valkyrie Reia is about to be executed by Duke, leader of the Dark Knights. However, Ariya, wielding Odin's Gungnir, appears on the scene. With unmatched strength, she easily lays low the demons on the scene. However, when she reaches the condemned, Reia unexpectedly steals Ariya's silver ring, the source of a Valkyrie's power.

Without her powers, Ariya is easily captured and also becomes Duke's prisoner...