Head Object

Head Objects are attributes that are possessed by some characters. They can manifest as objects, animals or marks. Characters that have a head object seem to see them as parts of their body as they are either unable to be removed or the affected person is unwilling to remove them. Furthermore, these objects may be able to change or act depending on the holder's mood or will. They may be unaffected by the laws of physics.

Origin
It is currently unknown why these objects exist or how to obtain them. Some characters seem to be born with them, sometimes inherited like in Majime's case while others obtain them some time in their lives like Shijima.