According to japanese beliefs, ōkubi appear as enormous, severed heads, which fly through the sky. In most accounts they are female in appearance. Quite commonly they have blackened teeth.

Ōkubi are little threat to humans. Their most common activity is to fly about harassing people: grinning at them, blowing away their umbrellas, or otherwise scaring them. According to some accounts, if an ōkubi breaths on any body part, that part will become inflamed. However, stories about serious injuries or deaths are rare to nonexistent.

Eyewitness accounts of ōkubi were common during the Edo period. In a story from Inou Mononoke Roku, the protagonist Inou Heitarō opens the door to his storage house. He discovers that an enormous head of an old woman — the size of the entire storage house — has taken up residence inside. Curious, he pokes at the head with a long chopstick. Instead of bumping against the forehead of the ōkubi, the head is sticky and mushy and the chopstick slides right in.