Corpse blade 1.

Armed with a gun and the mysterious Corpse Blade can Tsutsuki save his sister?

The first volume in the legendary Corpse Blade series, an action packed romp through a zombie infested Tokyo! School, chores, killing the undead — all in an average day for Tsuranuki Tsutsuki! After his sister is kidnapped by the zombies, this middle schooler sets out to save her, becoming handy with a gun — but he won’t be alone, as he encounters another kid on a quest, a mysterious high-school girl who can command the awesome power of the Corpse Blade!