Brigandine in the Wind

I, Akechi Yoshitaka, am a healthy male high-school student. When I was invited by a senior to infiltrate the dorm of Shizuru Girls High, for some reason we ended being chased by dangerous-looking female students wielding swords. One of the girls is actually my childhood friend, Tachibana Minori. In order to save me, that girl slashed at the other pursuers! Wh-what a thing to do! Then again, the girls are all okay. But, in exchange, the skirts are taking the damage and getting torn up...!? That's...