Injuu Gakuen EX ~La Blue Girl~

This novel is an adaptation of the Injuu Gakuen EX OVA.

Young ninja Midou Miko's fortune predicts that she's about to fall in love when an unexpected downpour throws her into the arms of Hidemasa -whom she immediately recognizes as the man of her dreams!

Poor Miko must not only stave off the jealosy of her friend, Fubuki Kai, but is forced to put her fantasies on hold when she learns of the ancient and mysterious 'male' and 'female' flutes which are wreaking havoc on her parents and women on Earth. Suspecting that the new man in her life might know something about the flutes, she must enlist his aid, or perish!

[From AniDB]