Shikabane-Gatana

Shikabane-Gatana is a battle-action manga following Tsuranuki Tsutsuki, a middle school boy living a mostly happy life, though his family situation is a bit unusual. His world is turned upside down when a massive disaster hits, and his younger sister is taken by zombie-like creatures. Determined to find her, Tsutsuki ventures into a Tokyo overrun by monsters. There, he crosses paths with a mysterious high school girl who carries an enigmatic sword. (Source: ANN)