Yūkimaru

is a young boy 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 and a gentle boy, probably due to his past, he constantly asks 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, Yūkimaru again bumps into Naruto, who offers for the orphan to join him in Konoha, to which Yūkimaru politely declines as he feels his place is with Guren. Soon after, Kabuto returns to conduct another experiment with Yūkimaru. He has Yūkimaru take several medical pills. Ultimately, this finally causes the Three-Tailed Beast to emerge.

Yūkimaru soon finds himself bleeding from the nose and ears before finally fainting, allowing the Three-Tails to break from Yūkimaru's control and go on a rampage. When Yūkimaru awakens to see Guren is fighting and losing against it, Yūkimaru, 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, Yūkimaru awoke to find a weaknened Guren, but happy she was still alive.

Unfortunately, Yūkimaru soon finds himself sick again, possibly because of the pills Kabuto gave him as speculated by Guren. After recovering again, Yūkimaru finds Guren fighting against Naruto, who are arguing about Yūkimaru. Yūkimaru quickly tells Naruto he is happy to have meet Naruto, because now he has a place to be; with Guren.

Later when Guren is in danger of being killed by the Three-Tails, Yūkimaru shows just how devoted he is to her by using his powers without the aid of Kabuto's pills to completely stop the Three-Tails's movements. Unfortunately, Yūkimaru's weak body finally gives out, allowing the Three-Tails to strike again.

After the beast escapes again, Kakashi and the other Leaf Ninja find Yūkimaru unconscious and bring him back to their hideout. There he was healed by Sakura and Ino. Upon awakening, he immediately looked for his crystallized flower and was happy to find that it was fine. He soon bluntly stated that Naruto and Guren are together inside the belly of the Three-Tails.

Strongly desiring to save both Guren and Naruto, Yūkimaru joined the Leaf Ninja in finding them. With his powers that linked him to the Three-Tails, he was able to locate the beast. There, he told the Leaf Ninja to bring him as many camellias as possible. The flowers were then dropped into the lake, where a whirlpool sucked them into the Three-Tails. Afterwards, Yūkimaru was sent to hide with Sai. Unfortunately, the enemies appeared again and captured Yūkimaru.

Taking advantage again of Yukimaru's feelings for Guren, Rinji convinced Yūkimaru to take Kabuto's special pills and use his powers to control the Three-Tails.

Yūkimaru uses the power to try and bring the Three Tails forth as he still believes that it will save Guren, until his energy runs out once more. As he collapses, Guren catches him, and he looks to her, relieved that his thinking of her brought her back to him. The two have a heartfelt reunion which is broken by Rinji, who begins to tell Yūkimaru of Guren's past grievances against him. Naruto tells him to shut up repeatedly--but Guren tells Naruto to let him be; and the truth of her past actions are revealed to Yūkimaru.

The boy is essentially speechless, and Guren admits that the fact of her murdering his mother is true. Naruto interjects, speaking on behalf of Guren, telling Yūkimaru how much she had changed; and that while the past Guren committed terrible sins, this Guren was regretful of her past trangressions, and would protect him with all she had and continue to think of him, even if he hated her. Guren continues to speak to Yūkimaru, admitting the same, and opening herself to him to kill her, if that is what he wished; but if he would forgive her, she would protect him forever.

Yūkimaru looks to Guren, and tells her that they both are who each of them should return to; and the two admit how much they love each other, sharing a tearful embrace. At this point, Rinji begins to attack, throwing scalpels at the pair. Naruto deflects them, taking one in the arm, and sending one back toward Rinji's face, slicing it. At this moment, Rinji tears off his own face and reveals who he actually is: Yakushi Kabuto.

Kabuto explains what Guren and Yūkimaru's purpose was: for the two of them to get close, and become dear to one another, so when Yūkimaru learned of Guren's murder of his mother, he would use his anger to make his power explode, though he is visibly surprised this did not occur. He continues to speak about the violent future ahead for the entirety of the Ninja World--and that being their reason for using Yūkimaru to gain the Three Tails.

Naruto begins to fight with Kabuto, and sends Guren with Yūkimaru, telling her to 'prove to him that she could protect him.' Kabuto laughs, yelling that they would not escape, and sends the animated corpse of Rinji to attack the retreating pair. Guren encases Yukimaru in her Crystal Release: Crimson Fruit, and tells him to wait for her; looking back at him in the same way that his mother did before she went to her death. Guren tries to use crystal style on the reanimated Rinji, but the sonic waves of the bats he controls prevents the crystals from forming; as well as shattering the protective crystal around Yukimaru. He attacks Guren, sending her to the ground in a fit of blood-laced coughing before turning his attentions toward Yūkimaru. But, before he can get an attack off, Guren catches his hands from behind, and encases the two of them in crystal. Though Yūkimaru tries to stop her, Guren sends herself and Rinji off the edge of the cliff they were fighting on into the lake, presumably to her death, as the crystal shatters on impact.

As he watches the crystal she gave him begin to crack, Yūkimaru, now filled with the sadness at the loss of Guren, lets loose his power, bringing the Three Tails into a frenzy, and shattering the seal the Konoha ninja were very close to completing. The Three Tails goes wild, and it takes a combination jutsu between Naruto, Gamatatsu and Gamakichi to stop its rampage. Yūkimaru falls unconscious from the strain, and Naruto retrieves him, looking out toward the water, and promising Guren he would keep the promise she could not keep. Clutched within Yūkimaru's hands, though, is the crystal-encased camellia, that has not fully broken. Yukimaru then was taken care by the Leaf Ninja until he ran away in search for Guren. The three are seen at the end walking away together

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.
 * In episode 101: Everyone's Feelings, while Naruto, Kakashi and Yamato discuss the situation with the Crystal Style user and Yuukimaru, Yamato refers to Yuukimaru's mysterious usefulness to Orochimaru as "the ability to synergize with a Tailed Beast."
 * Yukimaru's favorite flowers 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.
 * It is unknown if the ability to control the Three-Tails has been completely lost

Quotes

 * "Guren-san!"
 * What do you prefer ? White or red camellia ? "
 * "Guren is the place I can return to! "
 * (To Guren) You're a nice person Guren... You are the one I should return to, after all... and I'm the one you should return to, Guren. 
 * (To Guren) Uh-huh...And I will always think of you Guren. For now and forever... and ever...I love you.