SATAN 666

• JIO FREED
• Age : Start: 12, Rock Bird 13, Post-Rock Bird 17, Post-Armageddon ??
• Height: 145 cm (4'9")
• Weight: 35 kilos (77 pounds, 5¹/₂ stone)
• O-Parts: Zero, Shin Zero, Zero R, Satan(O-part on his left hand)

 BACKSTORY
The main protagonist of this story, Jio is a boy with great battle skill, great trust towards his friends and an ability to persevere, but he also has an obsession with money and is not soon to show his feelings, often hiding them or blaming other factors.
His dream is world domination, which other people often laugh at, calling it a child's dream until they see his abilities.
Jio started his life without friends, the people in his village forcing him to leave after the death of his only friend Jin's parents for which he was blamed. He was later trained in the wild by a wolf, known as Zero. However, after completing his training he was chased away again, giving him a chance to complete his dream.
His next friend, came in the form of Ruby Crescent, a girl in search of her father. At first, he helps her as a paid bodyguard, but leaves once she runs out of money. She ends up fighting a man claiming to be Satan, but the real Satan (sealed inside of Jio) easily beats him once Jio is knocked out. Once Jio is conscious again, he says he will follow her until she can pay him for saving her. He claims (in front of her) that he is only her bodyguard and nothing more, but Jio sees Ruby as a precious friend and even seems to have a crush on her. In chapter 45, he said that he was Ruby's lover and he also said he wanted to be near Ruby.
After having Ruby for a friend, Jio grows out to be more trustful, and slowly breaks away from his dream of world domination choosing to be more helpful and caring of others, quickly gaining more friends and meeting Mr. Wick and Mrs. Basil, which he sees as his father and mother (never having known his real parents). They were murdered by Kujaku, one of the Four Guardians of Zenom Organization.
In Rock Bird, Jio is defeated by Anna in the preliminaries but the officials allowed him to move up due to the demon inside of him. After Jio's last fight, Satan begins to awaken but Ruby calms him. Rock Bird's leader dubs Ruby his 'Key' and kidnaps her. An enraged Jio runs to the top of Rock Bird with Ball to rescue her. Jio finds Ruby on the wall with the 'Devil's Pain' curse placed on her. Jio defeats the leader, who was also a demon, but not before Satan takes control. Shin shoots a laser which causes all souls to leave their bodies. In order for Satan to survive Cross's attacks, he absorbs Ruby's soul and Ruby releases Jio. Ruby stays inside of Jio to protect him against Satan.
Post time-skip, he has become the leader of the cyclops village, and sets up a trade and supply route, next to sending 'some early cash' so that the village can survive, showing his leadership and skill with money. He currently is fighting Zenom together with the rest of the crew.
A running gag in the post time-skip is that Jio always seems to forget about Ball, although he remembers everyone else perfectly. During the assault on the Stea republic to rescue Ruby, everyone was split up in battle. After being reunited, Jio was relieved that both Cross and Mei were alright, but didn't seem to notice Ball (even though he was standing right next to them) What really made Ball mad was the fact that he didn't know if Jio was doing that on purpose to make him mad, or if he really does tend to forget him. One explanation is that Jio is confident in Ball's ability and doesn't worry about him because he knows his friend can take care of himself in battle.
After rescuing Ruby, Jio holds a conversation with her atop their ship. Apparently he had been trying to ask her out on a date, but whether Ruby accepted was never shown.
It is also shown that Jio is from another planet called "Eden" the same planet that all the recipes are from. It is also known that he is a special being that was created by Adam and Eve to Counter act the effects of the "Kabbalah"