Cardfight!! Vanguard G: THE PROLOGUE

Cardfight!! Vanguard G: THE PROLOGUE summary:

From the original author of Vanguard, Itou Akira draws the story of Chrono Shindou and his beginning.

One day, Chrono Shindou finds a Vanguard deck in his locker at school. With a clan never seen before called "Gear Chronicle", the gears of his fate begin to move.

The series was published in Monthly Bushi on December 2014 to April 2015, and later collected into one volume.  Serialized before the manga "Cardfight!! Vanguard G: Stride Generation" by  Raiti Hirakazu, which is an alternate story.