High School of the Dead

From the introduction: Zday at L-Location. You arrive in this world already enrolled in a nondescript High School, somewhere in urban Japan... The infection is worldwide, and within a week of the initial outbreak, even the President of the United States has been bitten (an infected soul got on board Air Force One). Pockets of resistance are sparse, and civic infrastructure is slowly grinding to a halt in the face of this catastrophe.