Shoulder-a-Coffin Kuro(2004)

Hitsugi Katsugi no Kuro. Kaichuu Tabi no Wa

Regularly mistaken for a boy and/or vampire, the traveler Kuro roams the land, clothed in black from head to toe, a Kuro-sized coffin on her back. Accompanied by her snarky bat friend, Sen, the mysterious duo meets all sorts of individuals en route - some good, some evil, some just plain crazy! But Kuro never stays in one place for long, begging the question: What exactly is she searching for? And what exactly does she intend to do with that coffin?!

(Source: Yen Press)