Ōga

is a former Inner from the organisation Kara.

Background
Ōga was the eighth Inner enhanced by Amado Sanzu. Her brain particular was modified to aid the scientist research about the human heart because he was on a dead end. When she tried to research the nature of Jigen's heart, he saw it as an act of treachery, forcing her to flee Kara but right before Jigen destroyed a part of her brain causing her to lost her will to live, soon after her body started to breaking down. Realizing that desires have a deep connection to life force and in the hope of reignite her desire to live, she began abducting many people for her experiments, watching their efforts as motivation and confronting them with dangerous situations so that they reveal their true feelings. Eventually, her actions prompted the Five Great Countries' Joint Investigation Team to investigate.

Personality
Ōga is an eccentric if not amoral woman. She is so fascinated by the concept of life and death, of how people are able to escape death, willing to mess with people's heads just to see how they will react. In her pursuit of researching survival instincts, she is shown to be very elaborate and methodical in her experiments. At the same time, she doesn't view herself as evil on grounds that she hasn't killed anyone. However, after witnessing Boruto's continued loyalty to others, she came to so remorse in her actions, willing to sacrifice herself to end the experiments.

Appearance
Ōga is a young girl of average height and fair complexion with big, red eyes. She has long, black hair reaching her lower back. As an Inner, she had the Roman numeral of "VIII" tattooed on her forehead and wears grey robes. While masquerading as "Yatsume", her hair is black and done up in an intricate style: She has ox horns on both sides with tight braids under them and two thick antennae hanging over her face. She wears a white bandanna to cover her Inner tattoo, a light blue, clipped-shut jack, and black shorts.

While masquerading as an old man, she used a puppet that appeared elderly man of heavily wrinkled, light complexion. It has a wide smile with several missing upper teeth, pupilless green eyes, scraggy white hair reaching his lower back with a long white beard. It wears brown cloths and a red cap with a yellow tongue and white wings on the side.

Abilities
As a former Inner of Kara whose body was modified with Scientific Ninja Tools by Amado, Ōga was regarded as being completely monstrous in terms of power and ability, with her abilities being viewed as superhuman. However, her enhancements are only mental, noting that she is not suited for battle. She is fairly strong, able to hold Boruto's and Shamo's combined weight with just one hand. She has a keen sense of smell, smelling blood on Rokuro.

Ninjutsu
Ōga is a skilled puppeteer, able to manipulate one disguised from a far. She has proficiency in Lightning Release, able to flow it into her weapons. She can use the Yin Release to project life-like images of people from afar. Her genjutsu can also produce elaborate stages to fool her targets.

Labyrinth Game Arc
Disguised as "Yatsume", she joined the Thunder Train with several passengers. Eventually, the wake up secluded in a room, Ōga introduced himself through a puppet of herself, claiming that they survived an accident and were exposed to a toxic gas. Ōga believed they had a subconscious ability to avoid death, and wished to test it. When one of the captives drew a death card, he killed them, stabbing them though their head with a puppet. Boruto attacked the puppet with Wind Release. Having made clear how serious his tests were, the first of five experiments began when a Kusa-nin angrily knocked over one of the scrolls, he accidentally activated the "Collapse" test, sending everyone to new location atop of a floor that hovered over a large chasm. Ōga explained that sections of the floor would quickly crumble away and they needed to escape to a higher, safe ledge. At the end of it, only 14 captives survived, and he congratulated them, allowing them to return and rest before the next test.

When Rokuro deduced that the Kusa-nin was actually Ōga's underling, he forced him into confessing it, resulting in his death. Ōga confirmed it indifferently when he announced the next experiment, Rokuro picking the "Light" test. The captives were presented with candles, and he explained the flames symbolised their lives, them dying if the flames went out. After providing them with lanterns to keep them and explaining how they could be passed around, he sent them off. At the end of the experiment, he intended them to try stealing each other's candles during a time-consuming portion. While the group containing self-centred people resorted to stealing others' candles, Boruto's group where they cooperated, exploited the wording of his rules to create a longer, communal candle, resulting in no deaths in that group. He was impressed by their ingenuity.

For the next experiment, "Pressure" was selected, which he found the harshest yet. It involved everyone trying to get into a limited number of alcoves to avoid the rooms' hazards, including a descending, spiked ceiling. However, the group discovered there was a hidden space under the floor, and they were able to use it to avoid being crushed. Ōga congratulated Boruto, as everyone surviving it would allow him to make the following experiments more interesting. Ōga complained that Boruto and Batta were late for the selection of the next experiment, "Calculation", and explained how they had to reach a gate within a two-hour limit after getting enough cards to sum 7, from cards numbering 1 to 8. When Kiseru and Boruto discussed about his deception, Kiseru realised Ōga's experiments were happening in genjutsu, and arranged for Boruto to wake up.