Izumo -Takeki Tsurugi No Senki-

Based on the H-RPG by Studio ego!
Yagi Takeru is a student who goes to the Izumo Academy.
He lost his parents when he was little, but he got adopted by Touma Rokusuke,
who is like a grandfather to him.
Takeru spends his days by getting kendo training from his grandfather and
being with his friends like his kendo rival Yamato Takeshi,his childhood friend Shiratori Kotono and her sister Asuka.
Because Takeshi isn't chosen as the representative for the kendo tournament,
he takes it out on Kotono, but starts to argue with Takeru instead when
Takeru and the others arrives.
While they are arguing, mysterious light and woman appears which suddenlly
causes faze shifting and blinding blue light emitting from Takeshi hands then body while he also screams in pain. They later wake up all scattered through the school and the school is covered in vegetation and infested with insect monsters and the town is gone.
After finding each others they gather in the schoolyard and while they are trying to figure things out, six big men in suspicious outfits appears and moves towards them.
They locate Takeshi and ones again the mysterious woman appears. She uses teleportation magic to kidnap Takeshi and Kotono. Then armed men on horses appears and attacks the suspicious men.
What does the future beholds for Takeru and the others in this strange world?