Tsubaki is Mizuki's lover. She claims that Mizuki used to be a sweet man, but ever since he got involved with Orochimaru, her relationship with Mizuki has faltered. When he escapes from prison she is able to help catch him. After she interrogates Mizuki about having a grudge against one who put his life on the line during Orochimaru's attack, Mizuki knocks out Tsubaki, who he apparently does not love anymore. After Mizuki was defeated, she mentioned to Iruka that she may have to face whatever consequences for her involvement with Mizuki. Source: Narutopedia
Isaribi was a human test subject under the control of Amachi who in turn used to work for Orochimaru. The test was meant to give shinobi the ability to breathe and operate underwater. Isaribi was one of the first test subjects, and was not the final version. She was sent back to the Land of the Sea to spy on the ships leaving port. Due to her bandages, which were used to cover the permanently scaled parts of her body, the villagers attacked her and vandalized her property. They feared and hated her as she was the only person to return from being "spirited away". Isaribi was promised that she would be returned to human form if she complied with Amachi's orders. To that end she attacked ships and killed a number of sailors under the disguise of the Kaima, a sea monster. Naruto was able to make her come to her senses, causing her to realize that were she to continue killing others to save herself, she would become a true monster. After his defeat, Amachi revealed that he never had a cure for her condition, and that he planned to dissect her once she was no longer useful. She returned with Naruto to Konoha after Amachi's defeat hoping that Tsunade can cure her.
Toki is the daughter of the late Daimyo Oowashi, twin sister of Sagi and the ruler of the Land of Birds. She lost all hope after her brother died, and nearly committed suicide, but Sagi's spirit stopped her, and gave her his stopped pocket watch, symbolizing her inability to move past the loss. She posed as her brother Sagi as the daimyo, and assumed the identity as the Cursed Warrior in order to kill Moso, the person who had assassinated her brother and father. Toki attempted to attack Oki, but was defeated, and resigned herself to death, seeing that she was unable to take revenge. Naruto, however, arrived and convinced her to live on for the sake of the Land of Birds before defeating Oki. After Oki's defeat, Toki's watch began moving forward again, symbolizing her ability to move on. The next day, Toki revealed her deception and apologized to the people of the land, but asked to be allowed to continue ruling the land to help restore it to its peaceful nature. The people forgave her and she continued to rule as Toki.
Hachidai was a miner in the River Country. He and fellow workers Sangorou and Rokusuke fled Katabami Kinzan when the homicidal practices of Kurosuki's Raiga emerged. On their journey away, a fierce storm knocked them off a mountain and they fell into a river below. The awoke far downstream in the Fire Country, where they were saved by Uzumaki Naruto. Hachidai then returned with his fellow workers when a squad was sent from Konoha to investigate the proceeding at Katabami Kinzan.