Seikimatsu Gakuen Densetsu Ouka 2 ~Zettai Seigi no Wana!~

At an elite boarding school, female students are abducted one by one.
When special teenage investigator Ouca Kamikaze learns her older brother Ginga has abused a power called the Way of the Unconditional Technique, she transfers into the school...

[from DLSite English]