Here are descriptions of the characters from The Demon Ororon. Most of them don't have pictures because I can't find any scans of the manga out there. The descriptions of the characters may reveal plot elements, so you may read some story spoilers.
Main Characters
Ororon Gem Farrel
Ororon is 123-years-old, the youngest of 7 sons of the king of Hell, but since his father died when he was 15, he has been the king of Hell. In Hell, some of Ororon's jealous brothers wanted him dead, and Ororon fled to Earth after an assassination attempt. He is taken in by Chiaki and very quickly comes to love her since she is one of the few people in his long existence to care about him. Ororon is cool and cold, and thinks nothing of wiping out someone's existence if it will protect himself and those he cares about. His killing hurts Chiaki, and Ororon bitterly struggles with the fact that Chiaki is repulsed by what he does. Ororon sees things simply as "kill or be killed". When Ororon was a child, his mother hated him because he reminded her of his father. When he was 10, his father became ill and chose Ororon to succeed him. Ororon hates Hell and the fact that he can trust no one there. He is tortured by the fact that Chiaki hates his very way of living.
Appearance: Ororon has short, light hair. His most distinctive feature are the 3 moles below his left eye. He's often seen smoking cigarettes.
Chiaki Saionji
Chiaki is a 15-year-old girl who lives on her own and doesn't go to school. She used to live with her grandfather, but he died when she was 14, and she now lives off the inheritance he left her. Chiaki is very lonely, her parents disappeared when she was too young to remember, and her only family is her friend Lika. One day she spots an injured man (Ororon) outside and takes him in. Ororon tells her he's the king of Hell and that for saving his life, he will grant her one wish. She simply wishes for Ororon to stay by her side forever. Chiaki is shocked when Ororon agrees, but is overjoyed to not be so alone anymore. Chiaki learns from Ororon that her father was the archangel Michael, and that she is a half breed angel herself, which puts her in danger of demons who want to eat her. Chiaki has always been able to see spirits and she now knows its because of her angel blood. When Chiaki finds that demons are out to kill Ororon, she is constantly shocked by all the violence that Ororon is capable of and begs him not to kill. Chiaki is traumatized by all the death and gore that soon surrounds her, and her astral powers awaken without her being able to control them. Ororon always tried his best to protect her, but somewhat unknowingly, Chiaki's disgust towards killing pushes Ororon away and hurts him greatly.
Appearance: Chiaki has short, light hair. She has a boyish body.
Allies
Lika
Lika is Chiaki's friend from school. She was one of the few people who didn't think Chiaki was a freak who could see spirits. She cares for Chiaki and doesn't trust Ororon to be near her. Lika is set to move away with her family soon.
Appearance: Lika has long black hair and is usually wearing her school uniform.
Shiro
Shiro is a cat demon who originally came to eat Chiaki, but was half killed by Ororon. Ororon restored him to health, and he now lives with Chiaki and Ororon. Shiro has a sharp tongue and often says hurtful things, but is actually loyal to Ororon and Chiaki.
Appearance: Shiro is tall with shaggy light colored hair. He has white cat ears and a tail.
Kuro
Kuro is Shiro's little cat demon brother. He follows his brother around and makes friends with cats, particularly Chiaki's cat Gomi.
Appearance: Kuro is a very small demon. He has light hair and black cat ears and a tail.
Miss Lucy
Miss Lucy is Ororon's maid from Hell. He brings her into Chiaki's home to cook and clean for them. She is one of the few from Hell who is loyal to Ororon and cares for him.
Appearance: Miss Lucy is old and has a wrinkled face. She keeps her pale hair tied back in a bun.
Othello Farrel
Othello is one of Ororon's older brother. He accidentally finds Ororon hiding out with the half-breed girl Chiaki on Earth. He stays with them, hoping Ororon will come back to Hell. When Ororon disappeared from Hell, Othello was the acting king, but didn't like doing it. He's one of the brothers that doesn't want Ororon dead. Othello is known for being a playboy but was once married the general of the Seiryu Army, a strong woman named Futaba. Othello was madly in love with her and Othello was heart broken when she was sentenced to death by his father. Othello then assumed the role as general of the Seiryu army and is widely known for his skills as a fighter.
Appearance: Othello has light hair and one mole under his left eye.
Yotsuba Farrel
Yotsuba is Othello and Futaba's son. He is the commander of Seiryu Army in Hell. He respects his father the general, but doesn't think he's a very good dad. He comes to Earth to assist Othello in bringing Ororon back to Hell.
Appearance: Yotsuba is young and has short black hair.
Charles Crodel
Charles is the Senior Counselor of Military Operations in Hell. He is very beautiful and highly respected by those in Hell and is actually quite an important figure. He comes to Earth to find Ororon.
Appearance: Charles has very long, pale hair and looks feminine.
Shinichiro Tachibana
Shinichiro is the Minister of War in Hell and comes to Earth with Yotsuba and Charles to find Ororon. He seems to be stressed out a lot by the kings absense and the current state of things in Hell.
Appearance: Shinichiro has black shaggy hair and stubble on his chin.
Garo Garon Ganimaaru
Garo holds the title of Holy Spirit of the Highest Rank and Office. She is summoned by people who want revenge against Ororon, but doesn't really wish Ororon any harm.
Appearance: Garo has long wavy pale hair and wears a robe.
Enemies
Mitsume
Mitsume is said to be one of the best bounty hunters around. He has a third eye, which invited endless abuse from superstitious villagers when he was growing up. His parents neglected and hated him. Eventually Mitsume fell into chasing bounties, when he comes across Ororon and the 2 million baron on his head. Its while chasing Ororon that he meets Othello, who insists on keeping Mitsume for himself as a treasured oddity. Mitsume is captured and kept prisoner by Othello, and Mitsume hates him with all his being.
Appearance: Mitsume has light hair, a third eye, and is missing his left arm.
Jyano, Ryo, and Ken
Some more bounty hunters that run with Mitsume. Jyano seems to be the leader of the group of bounty hunters. Ryo is a kid that looks up to Mitsume. Ken is just a lowly, depraved bounty hunter.
Appearance: Jyano has black hair hanging to his chin and smokes. Ryo has short black hair. Ken has shaggy light hair and glasses.
Oscar Ferral
Oscar is the third Ferral son and wants Ororon dead. He comes to Earth to find Ororon and get rid of him for good.
Appearance: Oscar has short black hair and wears glasses. He has a mole on his chin.
Orga Ferral
Orga is one of the elder brothers (the oldest?) and leads a rebel army called Klan Blue that is set to overthrow the capital in Hell. He apparently doesn't support Ororon as king.
Appearance: Orga has short black hair and has 3 moles under each eye.
The Dead
Ozu
Ozu (or Oz) was Ororon's father, the previous king of Hell who had ruled for 3,000 years. He was a cruel and arrogant ruler. He became ill and left the role of king to Ororon.
Appearance: Ozu had long pale hair and Ororon is said to look like him.
Sheila
Sheila was Ororon's mother, the reluctant mistress of the king of Hell, Ozu. She was abusive and mad and hated Ororon and his father. She once had a lover named Gem, but he was killed on orders from Ozu, which made Sheila hate him even more.
Appearance: Sheila had long black hair.
Matthew
Matthew was Ororon's trusted adviser in Hell, but he was put up to try and kill Ororon by people who kidnapped and threatened the life of his fiancee. Matthew hated hurting Ororon, but with his beloved's life on the line, he felt he had no choice.
Appearance: Matthew had long black hair that he kept tied back in a pony tail.
Futaba Hiiragi
Futaba was the former general of the Seiryu Army in Hell and Othello's wife. She was boyish and strong, and Othello was smitten by her immediately when he met her. She was challenged to a sword fight by Othello, and if she were to lose, she'd have to marry him. When Othello won, Tsubasa was apprehensive about becoming the wife of a prince of hell 10 years her junior, but she grew to love him as he loved her. She gave birth to their first child, Yotsuba. She was later sentenced to death by Othello's father Ozu when she refused to kill an innocent person for him.
Appearance: Futaba had black hair that hung to her chin.