Magic.
A century has passed since it was established as actual technology.
The two siblings enroll at a prestigious school for magicians called the National Magic University Affiliated First High School, better known as "Magic High School.”
Tatsuya, the older brother, is an “irregular” with a fatal flaw to his magic powers. The younger sister, Miyuki, is a star student with unmatched magical talent.

The two's student lives were continuous days of incident after incident.
Being attacked by the political association "Blanche."
The meddling in the Nine Schools Tournament by the Hong Kong crime syndicate the "No Head Dragon."
The Great Asian Alliance invading Yokohama.
The appearance of the monster parasites that alter the minds of the people they attach themselves to.
And the USNA army magician unit Stars' captain, Angie Sirius, also known as Angelina Kudou Shields, visiting Japan.

After a year full of turbulence, the duo's lives were slowly changing as they became second year students.
They were now living together with Minami Sakurai, who was sent to them by the Yotsuba Family, and Tatsuya has transferred into the newly established Department of Magical Engineering.
Though he planned to live a peaceful school life with Miyuki by his side, the world would of course not allow such a thing...
And once again, the curtain opens to a series of turbulent days.

[Source: official English website]