Vague Game Description by White Masq
I guess to grasp this game you should have some basic knowledge of what Valkyries are in Norse mythology. When a warrior dies in battle, a Valkyrie comes and takes him away from the land of Midgard to Valhalla. There the warrior proceeds to get drunk and fat and fight some more until Ragnarok comes along. Then these warriors band together with the Valkyries against the forces of evil. This eroge starts with an army of demons instead of the usual Norse forces of evil. The demon-king captures a Valkyrie and trains/brainwashes her to betray her sisters. Upon doing so, the demon-king is successful in stealing a ring of gold (that is apparently a source of the Valkyrie’s power). This causes the Valkyries to swiftly retaliate, and thus halts their previous pursuits of attaining warriors for the gods. When a few of the Valkyries become exposed, the demon-king swiftly captures them and orders a demon-knight (the protagonist of this work) to train/brainwash the lot of them. Seeing that the previous Valkyrie went so well, what with a small band accomplish?
"Shut the Hell Up, WM, and Show Me the Keywords": Valkyrie, Training, Yuri, Tentacle, Group Sex, Bondage