Kenichi Shirahama: While at first Sakaki does not want to take Kenichi as a disciple, this changes after the latter's fight against Tsukuba. After unwittingly scaring Kenichi by asking what his opponent stance was like and overreacting when he was told, Sakaki teaches Kenichi the Yamatzuki. Later, he is seen teaching Kenichi a way to defend and attack at the same time with his wrist, an effective tactic while fighting against many opponents. He has a high amount of faith in him, such as placing bets with Akisame about if he'll win and bets on Kenichi, though he will worry over his condition at times.During this time, he has taught his disciple many things, from how to defend himself against an opponent wielding a sword ( or any bladed weapon) to giving advice on girls. At the same time, he tries to be a tough teacher to Kenichi. He has to constantly battle his instincts, which means beat anything that so much looks at his disciple funny, sharing this attitude with Apachai, like when he had to be stopped by Ma Kensei from trying to fight Boris Ivanov after he attacked Kenichi without any warning.He has always told Kenichi that no matter how dangerous the situation is, he must come with him to observe and learn from his fights. However, he cares for Kenichi's well-being, such as telling him not to follow him to fight Hongo due to this time being too dangerous for him. However, he admires Kenichi's bravery to do dangerous situations, such as following him to watch his fight with Hongo and when Kenichi asked the soldiers in Tidat about Miu's location despite them being cruel to others. Sakaki is pushed to the point of rage when kenichi threatened or injured. Some examples are the mercenaries in Tidat and Hermit attacking Kenichi (and intending to kill him) after Miu's play. He actually poured a beer over the mercenaries head and asked "You actually dared to point your gun at my disciple, you little shit?" Sakaki seems to respect Kenichi's injuries in fair fights, however. He even call's him "my cute little disciple" has retured. He even went all out to commemorate that he and Miu had returned.
Jenny Grey: Sakaki sees Jenny as a close friend, though Jenny clearly and adamantly sees Sakaki as her fiance. This is due to a time when she was a child and a drunk Sakaki accidentally proposed marriage to her when she gave him a bottle of alcohol. Regardless, she respects him enough to let him go, suggesting she's moved on from her feelings for him.
Akira Hongō: Sakaki met Akira Hongō when they were in their late teens and both were considered rivals. Back then, they were considered good friends as Sakaki's sister stated he talked about him alot as a good friend. The two fought constantly in battles with each other, however, after being called by Yami for a chance to enter their organization, they (along with their friend Suzuki Hajime), were forced to fight to the death with each other. When Hongo killed Hajime, Sakaki cried and furriously fought Hongo, and the both gave them each others scars on their face, effectively becoming enimies. Their record for rematches is 125 to 126 in Hongo's favor . After their fight together when Jenazad interrupted their rematch, the two fought together to save Miu and agreed about their fight ending in a draw. By the time of their arrival in Tidat to save Miu and Kenichi, their relationship seens to have softened, such as getting along with each other. He even helped Hongo not fall over by letting him lean on his shoulder despite him saying he only did it cause he felt like standing there. Though Hongo refused Sakaki's help and said he still had to settle things with him, when Sakaki offered to settle things now the way Hongo is, Hongo merely chuckled and decided to fight him another time.
Nee-chan:This is what Sakaki calls his older sister. There is no real information on her at this time due to the fact that he really doesn't talk about his sister save for one mention where he comments that older sister's are scary after seeing Rachel comically beat on Ethan. Also that the only time he talks about her is in the flash back they have of him when he and Akira Hongo were younger and Suzuki Hajime, where she is shown riding a motorcycle, and appears to be very attractive to the point that even the normally stoic Hongo couldn't keep his eyes off of her beauty. His sister probably is a martial artist. In flashback Sakaki states that there is no point worrying about her during the fight. She, in turn, did not mind the armed gang arms dealers.