Yūrei are spirits in Japanese folklore, often depicted as the souls of the deceased who have not found peace. They are typically characterized by their white funeral garments and long, unkempt hair. Yūrei are believed to linger in the physical world due to unresolved issues, such as unfinished business or strong emotions like anger or sorrow. These spirits are commonly associated with traditional Japanese beliefs about the afterlife and are often featured in literature, theater, and art. Yūrei are thought to appear at night, and various rituals, such as Obon festivals, are performed to honor and appease them, helping to guide their souls to rest.