Yūkimaru

is a young boy (it is still unknown if he is a shinobi) who appears in the fifth Naruto Shippūden arc. He is a test subject of Orochimaru, because he has the ability to control the Three-Tailed Giant Turtle.

Personality
Yūkimaru is a quiet boy, probably due to his past, he constantly ask questions like "Is it going to be fun?". His main goal is to find home and is told by Naruto that home is a place where people think about you, which lightens his spirit.

Hunt for the Three-Tails Arc
When Sasuke Uchiha trains, he cuts off tree flowers with his Chidori. After that we can see Yūkimaru collecting the flowers. Sasuke tells Yūkimaru to go home. Yūkimaru replies he has no home to go to. Later on Kabuto sets off together with Yūkimaru for a journey. They eventually arrive at a dark swamp. There, Kabuto conducts an experiment where he forcibly releases the full power of Yūkimaru's chakra. This results made the Three-Tailed demon to partial emerge before submerging again. Afterwards, Yūkimaru is left exhausted, but Kabuto finds the results satisfactory. Later on the way back to Orochimaru's lair, Kabuto lets Yūkimaru take a rest at Yugakure, that Naruto is coincidentally at as well. There, Yūkimaru meets Naruto and they talk about bonds, making Yūkimaru glad that there may truly be a place for him. He then leaves a clueless Naruto to wonder who he was.

Later, he is sent out again with Guren to complete a mission. During which, he succumbs to sickness, forcing Guren to care for him. As a result, he seems to have grown attached to Guren and possibly vice-versa. This is further emphasized from how Yūkimaru reacted when Guren tells Yūkimaru she has to head out in a manner similar to how Yūkimaru's mother did before presumeably dying. He then gives her his necklaces with a special charm on it.

Later, Yukimaru again bumps into Naruto, who offers for the orphan to join him in Konoha, to which Yukimaru politely declines as he feels his place is with Guren. Soon after, Kabuto returns to conduct another experiment with Yukimaru. He has Yukimaru take several medical pills. Ultimately, this finally causes the Three-Tailed Beast to emerge.

Yukimaru soon finds himself bleeding from the nose and ears before finally fainting, allowing the Three-Tails to break from Yukimaru's control and go on a rampage. When Yukimaru awakens to see Guren is fighting and losing against it, Yukimaru, feeling certain that his place was with Guren, stood his ground and used his remaining strength to hold back the Three-Tails to give Guren a chance to escape. After he and Guren were washed away by a huge tidal wave, Yukimaru awoke to find a weaknened Guren, but happy she was still alive.

Unfortunately, Yukimaru soon finds himself sick again, possibly because of the pills Kabuto gave him as speculated by Guren.

Trivia

 * Based off his appearance, Yūkimaru looks very similar to the Three-Tailed Beast's former Jinchūriki, who was revealed on the title page of chapter 420. They have the same hair and eye colour (purple).
 * Another similarity with to the Three-Tailed Beast's Jinchūriki is their connection to flowers. In the splash page, the Jinchūriki carries a weapon with a flower attached to it, while Yūkimaru's first appearance is picking cut flowers.
 * Yukimaru's favorite flower are white camellias.
 * The capture of the Three-Tails in the anime is much more detailed that the manga because Yukimaru, Guren and the other sound ninjas were not in the plot; as well as in the manga, Naruto and the Konoha ninjas did not go on a mission at all. One blow from Deidara's clay bomb captured the Three-Tails.

Speculation

 * Due to his many similarities with the Three-Tails Jinchuriki, many fans have debated whether or not that Yukimaru is either a relative of the Three-Tails Jinchuriki or the former host himself and that he was revived somehow. It is also speculated that he is a Pseudo-Jinchūriki because he has the Three-Tails Chakra like Sora had the demon fox's chakra.