神装剣姫 アークセイバー～魔族懐胞～

The new threat to humanity has appeared, they are the demons. Their queen, Reginapis, is protected by the three beast officiers. Reginapis began her invasion to the human world to usurp a source of energy called Ark and to increase her race's population. Fighting against the prideful enemy that did not know defeat, humanity struggled against such a foe that their weapons could not leave a mark on. The longer the fight went on, the worse their situation got.

However, humanity still had one final plan. They gathered the warriors that can use the unknown energy of Ark, and succeeded in creating the humanity's protector, the "Ark Saber". 

Fuyunagi Tsubasa, Sefiria Grandir, and Yuno Plaftskya, three normal high school girls during daytime are actually Ark Sabers who transform and fight the demons when they appear. They fight in order to protect peace of humanity.

In order to deal with the Ark Sabers, the demons also started their own countermeasures. Sometimes the girls have to protect people, sometimes they fall into foul traps, and sometimes they are humiliated and brutally being used as lust relievers for the demons. Even though, the girls still believe in their conviction and choose to continue to fight. As they continue to fight, the girls' physical and mental wounds increase, but also the bonds among the three of them and their fates start to intertwine.

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