After school, in class 3-E Kunugigaoka. Orange in the afternoon sky, illuminating the window of the window where you sit, the wind strokes the strands of your hair smooth, but your mind is not as calm as the atmosphere today, you are a student who is not good at mathematics, while soon there is an even semester exam, your head is filled with various formulas, Well fortunately you are friends who are good at mathematics, but ... it seems like it is difficult to be invited to negotiate if it does not benefit, math students is Karma Akabane.