Gwishin are Korean ghosts who are similar to a Yogwi (요괴). Gwishin are people who have died, not monsters or creatures like Dokkaebi

Dokkaebi

Dokkaebi is a common word for a type of spirit in Korean folklore or fairy tales.The Dokkaebi is a mythical being that appears in many old Korean folktales. Although usually frightening, it could also represent a humorous, grotesque-looking sprite or goblin. These creatures loved mischief and...

. There are many in abandoned buildings, houses, cemeteries, forests, etc. They can be found almost everywhere. When a person who dies without completing something that they must do (e.g. revenge or staying longer with their family), their spirit does not go to the underground world after their death. Instead, they remain on earth until they have completed what they want to do. However, very strong gwishin do not go back to the underground world if they still do not want to go. These ghosts become stronger after time.

Legends

There are a lot of legends that are about Gwishin. Because they are common form of ghosts, children often make them up to scare others or parents tell stories to their children to teach them a lesson.
Most legends are about revenge, revenge for their families or about men who cheated or murdered the victim.
Here's a very famous ghost story. (Gwishin-iyagi (귀신 이야기)

There was a boy and a girl in a library, studying. It was very late and the boy decided to go home. With curiosity, the boy asked the girl, "Aren't you going home? It's very late," but the girl replied, "But I have no legs." With fear, the boy realised that the girl had no legs; blood dripped slowly, making a puddle on the floor.

Appearances of Gwishin occur in high schools, because schools in Korea can in a way have eerie atmospheres and look very abandoned at night time. They often have long, narrow, echoing corridors that are very dark at night. All the corridors are similar and there are many floors, which makes it scarier. The doors are wooden slide doors and in classrooms there are separate desks that are in line with other desks. In ghost stories, schools are the perfect place for ghosts to appear.

Physical Characteristics

Gwishin are usually transparent, legless and float in mid-air. Old gwishin usually have white Hanbok

Hanbok

Hanbok or Chosŏn-ot is the traditional Korean dress. It is often characterized by vibrant colors and simple lines without pockets. Although the term literally means "Korean clothing", hanbok today often refers specifically to hanbok of Joseon Dynasty and is worn as semi-formal or formal wear...

 (한복) which are worn for funerals. They have long, drooping black hair and sometimes they are faceless, depending on their personality. Male gwishin are somewhat rare, but they're like female ghosts, except female gwishin are more often heard.

Appearances

There are many, many ways they can appear.

Gwishin can appear as her/his true self.

1. They're seen floating, legless
2. Standing still, usually facing the person who is witnessing the gwishin.
3. Photographs or films, however 'Sponge
   Sponge (TV series)
   Sponge is a South Korean TV variety show that debuted in 8 November 2003 on KBS2. The show claims to be "infotainment," and revolves around presenting various pieces of triva in an entertaining fashion. The pieces of trivia are often sent in by viewers who wish to broadcast some piece of little...
   
   ' (a Korean show that presents true trivia facts) has proven that you can make a photograph by your own reflection.
4. Dreams
5. Reflections
6. Other creepy appearances shown in movies, television and comics

Gwishin can also appear to move things or prank you to get attention.

1. Objects falling down, clattering, moving
2. Physical contact with someone (e.g. pulling your shirt)
3. Objects missing
4. TV volume up or down
5. Something has changed, even though you haven't changed anything
6. They'll do anything to get attention, even if they have to flood your entire house with tap water.

When a gwishin approaches, the atmosphere changes most of the time.

1. Eerie
2. Wind, breeze
3. Suddenly cold
4. You feel something that is touching you (e.g. a cloth gently touching your skin, hair feels like it's being played around with)

Personality and Attitude

Gwishin have their own reasons to be on earth, even wanting to stay longer in a reason.
Depending on their personality and attitude, their strength and maliciousness can vary. For example, a very calm person who's always nice may not harm or bother other people. She/he will stick to her/his reason. A very aggressive ghost can harm people, even if they're a person. To become a gwishin, they must have a very strong urge to stay, or they will have to go to underground.
Here are some common reasons or why gwishin stays on earth.

1. Wanting to stay longer
2. Wanting to stay longer with someone (e.g. family, friend, even other gwishin)
3. Revenge for someone
4. Revenge for her/himself
5. Rampaging
6. Unsuccessful birth
7. Guilt
8. Prank or trick people
9. Other jobs to finish
10. Other reasons

Because they're ghosts does not mean their personality and attitude change. If they do not get a person's attention, they can become impatient. For example, they might want attention to send a message to a mortal human being, but if they do not understand or notice, gwishin may become a little aggressive.

Malicious gwishin who trick or kill people are extremely dangerous, yet no one has sighted one yet, however people spread rumors about abandoned places, mountains and forests. Schools is another place that ghosts can come out, but it is rare. However, students who suicided or were killed do appear.

Development

Gwishin, just like any other ghosts, become stronger as time passes. They learn to touch things and grab them. Because they're spirits who have no physical human body, their spirit body is transparent and goes through things. After time they learn how to touch and control things.

Sightings

Very old, ancient villages and towns very often have gwishin. There are at least one place sighting or witnessing of a gwishin in every place in Korea, since they are common. However, they may be rumors by people.
There are sightings that are accidents, for example a girl with droopy hair might look like a gwishin at first glance.