From MangaHelpers:
Saro Natsume, a high school girl, finds school terribly boring. She's already working part-time in a clothing store, and eagerly awaits her future in fashion, where she might one day have a store of her own. One night, as she is closing up shop alone, she is assaulted by thugs. She is rescued by a teacher from school, Yona-sensei, who suffers a stab wound but then heals almost instantly! It turns out that he's undead, a reanimated corpse who woke up with someone else's head stitched to his shoulders. Now Natsume is involved in this strange supernatural side of the world, and it looks like Yona-sensei is not the only undead person around.