A colourless world, a pure white world, a world where everything is filled with only one colour. What ought to be a young man's usual route to school - Sai was suddenly blown away, it was such an extraodinary world. There, he witness two young girls' fight unfold before him. One of them is a blonde girl he has never seen before, and the other is Mikage Mikuro, a senpai at his Highschool. Then, the blonde girl appeared as a transfer student before Sai, who has just returned to the original world. In order to grant her wish, she joined the battle game "Over Image" on her own and now she seem to have come to sought out Sai to be her campanion. "Two points. Are you my enemy? Or are you a harmless citizen?"