|Japanese VA||Mistuaki Madono|
|English VA||Jay Hickman|
"In the end, no one in our family could speak their hearts." — Hisanobu Sakamoto
Hisanobu appears to be a middle-aged man sporting a fair amount of wrinkles appropriate to his age, most notably around his eye and cheekbone areas. His hair sports a dark-brown color to it and is trimmed around the sides but is longer in the front and also usually seen slightly unkept. Due to a large amount of stress taken in from dealings with his family and employment, Hisanobu is usually seen to be somewhat stressed. Often enough, he is seen in almost every scene wearing the attire of a salaryman and rectangle glasses. However, later on, he is seen wearing a buttoned shirt with a vest over it and dark-colored pants during his visit to the hospital.
Much of Hisanobu's personality is seen through his concerns for both his wife Yukie and his step-son Ryōta. For Yukie, he is deeply concerned for her and attempts to do what he can to fill in the gap of their father and husband role in her family without worrying her. As for Ryōta, Hisanobu's relationship with him is often taxing for the both of them. Numerous occasions had Hisanobu attempting to become closer to Ryōta, sometimes through the discouragement of Ryōta's daily gaming, though this has led to Hisanobu being physically and verbally abused by the boy shortly after.
Overall, Hisanobu is often concerned for the health of those he cares for, even to the point of attempting to not worry them when he lost his employment and accumulated a debt, which he had kept to himself. At the hospital, he eventually concludes that he had not understood that each and every one of their family were suffering in their own way and that, like himself, kept these sufferings from one another. Thus, attempting to atone for his sins to save his stepson.
Not much is explained on Hisanobu's past other than events that occurred sometime not too long from Ryōta's kidnapping. His dealings with Ryōta are seen to be damaging to the both of them, which results in the physical and verbal abuse inflicted onto Hisanobu. It is also mentioned that he had lost employment and was not only seeking work but had accumulated a debt as a result, to which he says nothing to both Yukie and Ryōta in an attempt to not worry them. He also has an older brother, who is not introduced until much later in the story.
Upon arriving home late, Hisanobu discovers a nearly unconscious Yukie in the bathroom with the underside of her wrist slit open over the bathtub in a pool of water. It then becomes known that Yukie had attempted suicide. As Hisanobu rushes to her aid, she attempts to explain to him that not only had she had she known that he had lost employment but that she had been responsible for Ryōta's disappearance, though she fails to explain the latter. The man then proceeds to call an ambulance and then waits, keeping Yukie alive, and wondering what had happened between her and Ryōta.
As the story progresses, Hisanobu is seen visiting an unconscious Yukie at the hospital. Suddenly, he gets a call from his older brother who informs him to turn on the television. As Hisanobu does so, a scene from one of Ryōta's battles is seen, featuring Ryōta himself, Himiko, Sōichi Natsume, and Masashi Miyamoto. He then realizes what has happened between Ryōta and Yukie: Yukie had nominated Ryōta to be sent to the island. He then begins to understand that every one of them in the family had been suffering, and though there were attempts made to become closer, neither of them truly opened their hearts to one another.
Hisanobu later meets up with his older brother Nakaoka to discuss recent findings.  Nakaoka reveals the underground story of the Schwaritz foundation and the ambitions behind the foundation: World domination through the application of the concept of Panem et circenses. As the two are further into the discussion, Hisanobu's older brother suggests that Ryōta may have been intentionally chosen for nomination to the real-life Btooom! game, but not aware of the foundation's plan. Following up with his theory, he suggests to Hisanobu that they investigate Ryōta's computer to find evidence to fight the company with. However, they must hurry because the foundation had the island filled with self-destruction bombs within that area, as Hisanobu and his allies have over 20s hours left. 
Unfortunately, he and his brother are trailed by the foundation's assassins. Nakaoka is silently shot by one of the assassins, including his own private laptop.  Luckily, the USB containing information about the foundation's evil plot isn't destroyed, as Hisanobu is given by his dying older brother the USB, and to find the nearest computer to upload the information across the network. Though Hisanobu was surrounded by two foundation's assassins to have the USB destroyed, he uses his tactic, using the bag of his dying older brother as a decoy, then managing to run into the nearest high security office building.
When the workers at the high security office see blood on him, as if he had murdered someone, Hisanobu tries to explain the truth about the foundation, as well as being chased by one of the foundation's assassins trying to kill him. He asks them to borrow one of the computers to upload the information for the greater good. As the workers refused to let him borrow one of the computers, Hisanobu has no choice but to forcefully find one, thus managing to upload the information completely across the world before the two assassins arrive shortly, and Hisanobu is released by the workers who attempt to stop him from spreading the truth about foundation.
Once the plan had gone smoothly, Hisanobu later goes to Tyrannos Japan where the leader of foundation arrived there, helping Iida to raid on the gaming company's building. With the help of Iida's colleagues, Matthew Percier, who is currently with his agency's team to rescue Ryota and the other surviving Btooom! players, at the same time he hacked into Tyrannos' network within its main building to kill whoever attempts to swear their loyalties to the foundation, carries out dirty tactics like killing both Iida and Hisanobu, and attempting to hack into the systems like killing those Btooom! players and initiating the self-destruct immediately, but was too late because the foundation had sent their mercenaries to kill all surviving players at the same time Matthew and his team got near the island.
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