Kiseru Gankubi

is an Anbu from Konohagakure. He is an undercover agent as an Outer of Kara.

Background
Kiseru claims he was born in a mountain village near the border with Takigakure, where he enjoyed hot springs with his grandfather, though he later admitted this was a lie. He eventually moved to Konoha, where he became an Anbu and met Konohamaru Sarutobi. At some point, he became part of a multi-village team investigating several mass disappearances alongside a treasured friend.

Personality
While undercover, Kiseru is a feisty and determined individual, refusing to give up trying to escape despite making no progress. He is compassionate, readily collaborating with Boruto to help the civilian captives survive Ōga's experiments and urging Boruto to remain positive after some of them died, stressing they did all they could. Because it was part of his mission, he withheld that he owned a working communication device. When he came under suspicion of working for Ōga, unable to reveal his mission, he became more aggressive and cold, to the point Yatsume grew scared of him. His Anbu team-mates have expressed concern for his mental health over the solitude stemming from the prohibition to reveal his identity and mission for an extended period of time, having to suspect everyone and in turn being suspected by everyone. He is willing to undertake a dangerous mission to find his friend.

Appearance
Kiseru is a fairly tall teenager of tanned complexion. He has dreadlocks reaching his shoulders tied in a ponytail. He also has stern eyes with blue irises and thick brows. He wears a white undershirt with his forehead protector on his pouch attached to the left side of his waist, a grey vest, and grey pants with black sandals.

Abilities
As an Anbu, Kiseru is a highly capable ninja. Even when outnumbered by other competent shinobi, he is able to overwhelm his opponents.

Ninjutsu
Kiseru is quite skilled with Fire Release, able to produce blasts, arrows, or flame-enhanced punches. He can cover himself in flames, using them to overwhelm nearby opponents. His flames can quickly burrowing through the ground and instantly incinerate kunai. He is partial to using the large flames of his attacks as a smokescreen to sneak in close to his opponents for incapacitating strikes. His Anbu team-mates consider him to have advanced medical ninjutsu skills.

Physical Prowess
He can jump several feet in the air quite easily. He has great stamina and pain resistance, attempting to break out of his confinement for quite a while, and being unbothered by his swollen hands after trying to punch his way out. He was bothered, but otherwise unharmed by Yatsume's Lightning Release, even though they were both on water when she attacked him.

Intelligence
Having infiltrated Kara, Kiseru is a capable spy. During Ōga's experiments, Kiseru consistently acted as if he was showing his hand by revealing his Fire Release, but in fact held back how strong he actually was. When having fight against superior numbers, he quickly took advantage of the location to separate them in order to defeat them one-on-one. Kiseru is quite attentive, having seen through an injury Rokuro had tried to conceal since before Ōga's experiments began. He is good at improvisation, using the railing of a safe platform to create a ladder. He is also very persuasive, convincing his superior to allow him on a mission despite his personal attachment to it.

Labyrinth Game Arc
While on the Thunder Train, Kiseru and all other passengers fell asleep and woke up detained in a secluded room. Kiseru attempted to break out by attacking the walls with Fire Release and taijutsu, with no results. He recognised Boruto, identifying himself as a fellow Konoha-nin. Ōga revealed himself as their captor, and announced he'd put them through experiments to test their ability to avoid death, putting them through five tests before they can leave his maze. After the "Collapse" test was chosen, the group was teleported to atop of a brittle stone floor floating above a massive chasm, requiring them to reach a safe platform. He and other shinobi attempted to attack Ōga, who turned out to be a projection. Concerned by the others still on the platform, Kiseru grabbed one of the rope barriers and lowered it as a makeshift ladder for them to climb. He was sad they couldn't save everyone, but assured Boruto that they did the best they could.

While waiting for the next experiment, Rokuro attacked a Kusa-nin, accusing him of being Ōga's minion. Kiseru recognised the merit in the accusation, recalling how he had pushed him when Kiseru was near him at edge of the falling platform before it began crumbling. He died from Rokuro's jutsu asking for Ōga's help. Ōga arrived and sent them into the next experiment, which involved candles connected to their lives. When the group who decided to work together came across a closed gate, Kiseru and Namua trusted someone else to hold the lanterns with their candles to help Boruto force it open. In the next room, he along the other shinobi helped protect the non-shinobi from a dust storm while they protected the entire group's candles, and informed Boruto that Shamo had gone ahead with a woman he liked. Near the end, they had to take a slow-moving elevator, and realised that their candles wouldn't last the entire ascent, Ōga intending them to steal each other's candles. Boruto exploited the exact wording of Ōga's rules to make one long candle with the remains of everyone else's, shared by all, so they all survived the ride, clearing the experiment.

Before the next experiment, Kiseru warned Batta against trying to sacrifice him for her benefit, and when the group discussed their dreams, Kiseru wanted to soak on the hot springs in his home village. When Ōga arrived, Kiseru picked the next experiment, which took them to an empty room. Kiseru was annoyed by Shamo's agitation when Namua discovered bloodstains on the floor. When Shama triggered the ceiling to start coming down at them, and several other hazards in room, one of the switches revealed alcoves where they'd be protected. Kiseru fought Rokuro over one, his Fire Release endangering others, requiring Boruto to put it out with Water Release. When the water drained, Boruto realised there was a hidden space under the floor, and Kiseru was among those who helped Boruto break it open, the extra space helping no one die in the experiment. As they left, Batta bumped into Kiseru on her way to talk to Boruto, and confided her suspicion of him being Ōga's subordinate over a working communication device he kept hidden, which she pick-pocketed when bumping on him.

While waiting for the next experiment, Kiseru was among those who noted Batta and Boruto were taking a long time returning. By the time they returned, the "Calculation" experiment was picked, in which each person received a card with a number from 1 to 8, and they had to reach a gate within two hours with enough cards to sum 7. Kiseru's was 7, and he decided to contact someone, realising his communication device was gone, and that Batta had stolen it. By the time he reached the gate, Boruto was there waiting for him.

Boruto confronted him, and questioned his trust in Rokuro's word about Batta's death. He ran off and attempted to communicate with device, to no avail. He offered Boruto his 7 card, but Boruto refused it. Rokuro, Yatsume, and Shamo caught up with them, so he escaped underground, digging with his Fire Release. He fought from the shadows until Rokuro baited him by putting himself in a vulnerable position. Rokuro attempted to control him with his jutsu, but Kiseru pulled the parasite out before it could get in him, and burned through the others, striking Rokuro in an injury he failed to conceal from him. Boruto's Vanishing Rasengan caused him to retreat. He targeted Yatsume, resisting her Lightning Release, and retreated again from Shamo's Earth Release, dropping a scroll containing details of his mission. When Boruto accused everything about him being an illusion, he realised the entire maze was a genjutsu, making sense of his friends' intel. Shamo intercepted his attack on Boruto, giving him the scroll. He explained that he couldn't trust anyone after being framed for Batta's death, and stabbed Boruto, using a jutsu to make him wake up from the genjutsu, before collapsing himself.

Ultimately, Ōga was revealed Yatsume, who was convinced by Boruto to free everyone from the genjutsu prison. As everyone emerged from their captivity, Kiseru was delighted to find his friend alive and well.

Trivia

 * Written as 煙管, "kiseru" is a type of Japanese smoking pipe, while his surname indicates the shank of the kiseru.