Natsuki Shimazu

Natsuki Shimazu (, Shimazu Natsuki) is the third son of the Shimazu Bushi's leader and the youngest brother of Haruhisa Shimazu and Akihiro Shimazu.

Appearance
Natsuki is a young man of average height with medium-length orange hair and purple eyes. He has two spiral piercings, one on his right eyebrow and one on the left side of his lower lip. His attire consists of a light-colored shirt and a dark-blue, undivided hakama. He wears shin guards, made of iron plates attached to the cloth. He has his Kitetsu Swords fixed on his platformed sandals. When he served under the Uesugi Alliance, he wore the White Corps' uniform, a white cape with the Uesugi mon on the back.

Awaji Island Recapture Operation Arc
At Harima port, as the Uesugi Alliance gather, Haruhisa asks Natsuki if he remembers what their father said and Natsuki confirms its that whoever takes the Kishin horn in Awaji will be the next clan head. Fuyuie is sure that Akihiro can do it.

The Shimazu bushi are put in the same squad with the Amako bushi, Musashi and few others. Katsumi suggest they decide the leader with a battle and Shimazu choose Akihiro, who then easily defeats Katsumi and Musashi to become leader. Later, when the ship gets attacked by oni, the Shimazu link up and manage to defeat some oni. Later, when Musashi and Michiru are suspected to be involved with the enemy, the Shimazu squad is left behind until Musashi's involvement is cleared, so is soon cleared as the enemy bushi attack and Musashi is revealed to be the Obsidian Goddess.

Later, Kuroko forms a plan and sends the Shimazu to assist Musashi and destroy the Yura Mine. As the Shimazu arrive, they see an oni protecting it and link up to destroy it. Shiro shows up, but so do Naotora and he defeats Shiro. As part of their next mission, they need to find and defeat the third enemy Bushi, however, Akihiro wishes that they destroy one of the Kishin's horn. Proceeding, they team up with other Bushi and see Yataro, who then states he merged with the Kishin and turns into an oni. The Shimazu attempt to link up to defeat it, but with his barrage from the swords, Yataro manages to always break their link. Akihiro grows inpatient and when Natsuki gets cut off, he just notes that he is always slow, however, Musashi comes and saves Natsuki. Musashi then proceeds to help other Shimazu, while also destroy swords, allowing them to finally link up with Akihiro, who then destroys the horn of the oni.

However, as that doesn't defeat the oni and it proceeds towards the Kishin, Musashi wants to form a plan and the Shimazu agree, revealing they have accepted him. Akihiro isn't looking happy and explains that they shouldn't be happy as they failed to kill the oni and now their comrades are in danger. Haruhisa gets angry and explains that Akihiro only cares about himself and getting the heir to the clan. He doesn't care about the rest and is fine if they die. As Akihiro confirms it, Haruhisa slaps him and states he won't be following him anymore. Akihiro takes something from his pocket and throws it out. Musashi picks it up and asks Fuyuie what it is and Fuyuie explains its a wooden piece used in planning battles, and that the Shimazu brothers did the same when they were young and shared their dreams. Haruhisa calls Musashi to be their final chain in the link and as they attempt to link up with him, Akihiro tries to steal the link, which only annoys the Shimazu for his greed. Musashi apologizes, stating he shouldn't have taken his place and that his dream is to defeat oni with his brothers. Recalling their past, Akihiro didn't want to be the final chain, but Haruhisa, Akihiro tells Musashi that he is wrong. Akihiro manages to steal the link and attacks the serpent, knocking it out for a moment, but the serpent later continues.

Akihiro then orders everyone to line up and link while standing still. That offends the Shimazu, but Akihiro states that's the only sure way they will link with others. They all link up and Akihiro heads towards the serpent, noting to himself that this way his brothers are safe. As he reaches the horn, Orochi ends up swallowing him and the serpent. Uesugi Bushi tell the group to run as Orochi will power up and wipe them out. Musashi approaches Haruhisa, telling him that older brothers protect younger, but Haruhisa reveals he hates Akihiro and if he had a red soul, he would had led them better. Musashi then wonders if he wants Akihiro to die so that Haruhisa can lead them. He then gives him Akihiro's wooden piece. The Shimazu recognize it and realize that Akihiro is hung up on the past. Haruhisa then decides to go and save him. A bit later, the other Shimazu and Musashi also enter Orochi and reaching Akihiro and Haruhisa, they hear that Akihiro mentions the link is broken, but the state they will just link again. They link up, but Akihiro is exhausted and fails. Musashi suggest that he takes his place, but Akihiro refuses, otherwise he has no use for the Shimazu and his life would be meaningless. Haruhisa states he forced all that on him, but what really matter is that they are brothers. They link again and this time Akihiro breaks the serpent horn.

With the Orochi nourishments cut, the Bushi manage to cut Orochi's horn and defeat it. An Uesugi bushi asks the group who cut the serpent horn as that saved thousand of lives. The Shimazu brothers point at Akihiro, but he doesn't want the reward and states someone else should take it. Haruhisa tells him that he fought harder than anyone else and the Shimazu brothers will be part of all kind of legends now. Haruhisa also tells Akihiro to thank Musashi for finding his wooden piece and Akihiro promises to repay him.

Kitetsu Sword
Natsuki’s Kitetsu Sword is a two-piece weapon worn on his legs. It consists of two pivoted black blades, an inner and an outer blade, folding in and out of his sandals.

Etymology

 * The name Natsuki means "summer" (夏) (natsu) and "tree" (樹) (ki).
 * The first character of his given name means "summer" (夏, natsu). In the name of his brothers, the first character also signifies a season.
 * His given name would have been Natsutoshi.

Trivia

 * He and Tokisame and Tadayuki are double cousins, as they are cousins through both parents.
 * Natsuki's ideal type is someone with a pretty face.