Science and magic exist side by side in this world.

This is the peak of the science side with a curriculum for espers, Academy City. In this city where 80% of the population are students, the season has finally come when all residents are excited and fidgety!

It's Christmas Eve.

Amidst the city showing a cheerful hustle and bustle, ordinary boy who can’t keep up with school, Kamijou Touma, also doesn’t intend to miss this event! He was hard at work in his supplementary lessons...

A backward glance from the default misfortune-prone bastard, the silver-haired sister freeloading in his dormitory, Index, in the heart pounding scene different from the usual, activates a new gluton skill!? While Kamijou tries to desperately stop that, Misaka Mikoto taken in by the Christmas Eve atmosphere appears before him.