Former leader of the Nadeshiko Village. Decades ago she encountered Jiraiya who has entered her village to do "research" for his next novel. After he escaped she pursued him and challenged him to a duel for his hand in marriage. This match was however postponed, as neither party was making headway against the other. Jiraiya promised that their students instead should one day seek each other out and fight if the two never met again. This promise fell to her pupil Shizuka and Jiraiya's last pupil Naruto Uzumaki. She's presumed to be Shizuka's mother but is not confirmed neither named as such in the credits, instead she's named as "Previous Head of the village (先代里長)". Appears in episode 235. (Source: Narutopedia)
Yukata (ユカタ, Yukata) is a young kunoichi from Sunagakure. Anime Debut: Naruto Shippūden Episode #261 (source: Narutopedia)
Suiren (スイレン, Suiren) was a kunoichi of Kirigakure. Ten years prior to the formation of the Allied Shinobi Forces, Suiren was part of Ganryū's team that was tasked with retrieving a scroll along with a team from Iwagakure taken by Kumogakure shinobi. After retrieving the document, Suiren was excited for the prospects of peace that a mission like this would bring. She was however wrong as Iwagakure betrayed them. After Junsai was killed, Suiren sacrificed herself in order to protect Ganryū. This incident which come to be known as the Tragedy of Yosuga Pass marked the begining of hostility between Kirigakure and Iwagakure. Suiren was a kind and loving person who dearly held onto the ideals of peace. After their mission was seemingly completed she spoke openly of what an alliance like this between Kirigakure and Iwagakure would mean for the shinobi world. She was a very beautiful kunoichi with brown eyes and long blonde hair with two strands framing her face. She wore a pair of earrings along with the standard attire of the Kirigakure-nin complete with forehead protector and flak jacket, along with the jade-green bangle that was worn by her team. Source: http://naruto.wikia.com/wiki/Suiren
Shiseru is an officer from the Hachou Village. Anime Debut: Naruto Shippuuden Episode #290 (Source: Narutopedia)
Tekuno Kanden (感電テクノ, Kanden Tekuno) is a shinobi of Konohagakure that protected its borders after the Invasion of Konoha. Tekuno has a robust build and has shaggy brown hair. He wears the standard attire of a Konoha shinobi along with fingerless gloves. He also wears his flak jacket unzipped under which he wears a utility sash with his several scrolls. His abilities primarily revolve around the use of heavy explosive artillery and is also highly skilled at setting traps. He was also very skilled at using wires, often incorporating them into his traps. He was so proficient with them that he is able to lay them all over the battlefield then manipulate them in such a way that he could trap multiple enemy in them at once. During a mission he was shown summoning a crossbow that he used to fire projectiles with exploding tags attached to them. Along with this weapon he also summoned a few katana, so it can be assumed that he is skilled at using them. He was assigned to a squad along with Hayama Shirakumo, Kosuke Maruboshi and Naruto Uzumaki to protect the norther boundaries of the village after Suna and Otogakure's invasion of the village. During their mission he was assigned to set traps around the area. Not long after they were ambushed by a battalion of ninja from Iwagakure. Tekuno's traps proved useful in hindering the progress of the ninja but when they had breached these securities, he stayed behind to allow the other members of the squad time to escape and report to the village. He summoned a crossbow with explosive tags attached to the projectiles and along with Hayama wiped out the majority of the ninja. Together the team was able to wipe out dozens of Iwa ninja. He was later seen helping to restore the village after Pain's Invasion bragging about his heroism on the mission.
The Country of Mist has had its share of civil wars and has always used their Shinobi with Advanced Bloodlines as the primary weapons. Over time, those with "Advanced Blood" came to be hated and feared. This forced those with advanced bloods into hiding in order to live in peace. Haku was one of the few people in the Mist with Advanced Blood left. When Haku was just a young child, his father discovered that his wife was part of an Advanced Bloodline. Haku's father proceeded to kill his mother and then went after him. In Haku's fright, he killed his father and fled his small village, believing himself to be a monster: a monster loved by no one. On one faithful day, Haku looked up in the slums of the back alley to see a Shinobi staring down at him, this Shinobi was Zabuza. Haku then proclaimed, "You have the same eyes as me". Zabuza realized that Haku was one of the Advanced Bloodline limit carriers, and took the child under his wing. Haku was raised by Zabuza as "a tool" to be called upon when needed in exchange for his "freedom" from the slums. He learned how to use his unique abilities and eventually became a Hunter-Nin. When Zabuza's plan to kill Mizukage fails, Haku fled the village along with Zabuza to fulfill his job as a veritable "a tool." Haku's slender frame and delicate appearance enables him to disguise himself in various ways. In fact, while finding medicine to treat Zabuza's wounds Haku runs into Naruto. Naruto mistakenly believes Haku is a girl. As we see in the ensuing brawls, it is not appearance that determines strength. Rather, under that soft face we see that Haku has an adroit knack for speed and Jutsu skill. Combined with his knowledge of the human body, Haku can target his opponent's vital organs and kill them instantly using pinpoint accuracy. The main choice to attack these vital organs is with simple needles that are used by physicians in the battle field. Haku's bloodline originates in the country of Mist so it is no surprise that his Jutsus are water based. His "Flying Water Needles" is a technique whence he uses his chakra to create ice needles via water on the ground. Furthermore, he uses his chakra to control the path of the needles and strike the enemy. His other technique, "Demonic Ice Mirrors" uses water to create ice mirrors to surround the enemy. He then combines himself with the mirrors and uses the reflection to transport himself from mirror to mirror while attacking his enemy from all angles. His most incredible ability however, is the ability to do one-handed seals. This allows him to complete various tasks that are not capable of being accomplished without having a free hand. Although Haku is an exceptional fighter, he is a kind ninja who is saddened by unnecessary death. His fighting spirit comes from the will to protect his most "precious person," because "when a person has something precious to protect, that is when they can become truly strong." Haku is later 'revived' by Kabuto using Impure World Resurrection during the fourth shinobi world war.
Jir�b� is the physically strongest member of the Sound Four. Through simple physical attacks, he can defeat an opponent in one or two blows. Because he is able to absorb the chakra of others, Jir�b� often captures opponents so that he can absorb their chakra as a form of sustenance.