Tensi Academy is a school lead by a twisted person. It's an all-girl school where you could become a sword-bearer, and then fight against another sword-bearers, and climb the rank to become the first rank. Should you attain the first rank, the leader (or director) will grant you any wish (let's say that the director is kinda Bill Gates in our world). And by climbing the ranks, you will also attain money and social status.

The sword-bearers fights in pair (called heaven and earth sword). They must fight using swords, fight in controlled environment (there are rules and how-to-scores and such), and supervised by special judges. Only Heaven sword could make a score (by defeating other heaven swords). Earth swords couldn't make a score but could help Heaven swords like by defeating other earth swords (so they won't get in their heaven swords' way). The fight ends when the Heaven sword could make a score (defeating other heaven swords). The scores is then accumulated and counted into ranks.

The protagonist is Kurogane Hayate. Carefree, idiot, have yuri tendency, but also very kind. She is a "secret" substitutes of her twins, Kurogane Negi, a prodigy of Kurogane sword style (Hayate herself is a Dan 3 in Kendo but she quits kendo middle way for some unknown reasons). She intends to live peacefully and lay low until Negi could take back her place... but the orphanage where she used to live at is in huge debt (8 million yen) and will be demolished if she couldn't pay. So she's forced to reach the first rank (to get the money prize).

Her partner is Moudo Ayana, an unsociable and brutal meganekko. Fortunately for Hayate, she's smart and together, Ayana and Hayate would fight against other sword-bearers to reach the first rank. Ayana have reasons to help her, but if you want to know, you'll want to read it yourself ^_^ I want to avoid spoilers.