Yūkimaru

is a young boy (it is still unknown if he is a shinobi) who appears in the second Naruto Shippūden filler arc. He is a test subject of Orochimaru, because he has the ability to control the Sanbi.

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 and he 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 in a strange creature (possibly 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 a hot springs, 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.

Trivia

 * Based off appearance, Yūkimaru looks very similar to the Three-Tailed Beast's former Jinchūriki, who was revealed in splash 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 first appearance is picking cut flowers.