First appearance: Battle 7
Age: 29-30
Height: 192cm
Weight: 110kg
Type: Dou
Type: Katsujin Ken
Martial Arts: Karate (specializes in Mutenkendoku-style)

Sakaki Shio is infamously known as the 100-Dan Street Brawler of Karate and is one of the masters of Ryozanpaku. He claimed not to take disciples at first, but gradually grew to like Kenichi and is always eager to train him. He has a soft side which he tries to hide behind his tough guy attitude, and is usually the one worrying about Kenichi the most despite acting like he does not care.

Sakaki is arrogant, violent, and a drunkard, but is quite possibly the most normal of the masters at Ryozanpaku. Sakaki is a very intimidating person even when he tries not to be, something that he doesn't seem to realize and is put off by whenever someone points it out. This persona belies a kind and somewhat caring nature which he tries (and fails miserably) to hide, though he is somewhat hot-blooded and short-tempered. To this end, he could be seen as a bad liar, pointed out by Kenichi at one point when Sakaki tells him to lie about the money he received from the underground fighting tournament.

Amusingly, it is shown that he suffers from stage fright and becomes extremely flustered at being the center of attention, such as when he was posing as Miu's father during a parent-teacher interview and when he was forced to train little children. He's not very good when it comes to children, as due to his intimidating nature, he caused them to cry. However, when he tried again, he at least managed to warm up to them eventually and remember all their names and they all liked him a lot.

However, out of all the masters, he is the nicest when training Kenichi. He's usually the only one who worries over Kenichi's condition in a fight or when he's left alone. Though is usually hard and indifferent towards him, it is because he cares for him and needs to be hard on him in order to push him. Sakaki also tends to be impressed whenever Kenichi impresses him and makes a remark by rubbing his finger under his nose whenever he's moved by his actions, often wondering when did he become such a man.

In his younger days, Sakaki was the disciple of a Sei-type master of karate. Sakaki's only known relative was an older sister who would constantly look after him. While he took his training seriously in various styles of karate, including his master's Muntenkendou-style, Sakaki's relation with his master was strained. His master was a member of Yami and was teaching Sakaki the "true styles of karate" so Sakaki could succeed him in joining Yami but Sakaki was against killing.

Also at some point in his life, he met Hongou Akira and the two became good friends and strong rivals, constantly having matches and stopping thugs together. During Sakaki's late teens, he met Suzuki Hajime, who asked to be his disciple despite only being a few years younger. Naturally owing to his dislike for taking on disciples, he refused, but was still followed by Suzuki. When finding Hongu attacked by thugs, Suzuki showed noticeable skill by saving Hongou from bullets. Sakaki and Hongou quickly grew to respect Suzuki and ultimately become friends. Suzuki would constantly referee their matches, leading Sakaki and Hongou to have a tie score of 125 wins each.