Soma's face is modeled after his voice actor, Hiroshi Tamaki. He is of above-average height with a lean build, pale skin, short dark brown hair with medium-length bangs neatly parted to the right, and brown eyes. He also appears to have multiple healed piercings in both ears.
Soma's signature attire consists of a dark gray windowpane pattern three piece suit, a black button-down shirt with white buttons and red stitching, and a pair of black and brown leather dress shoes with tan soles. Due to his dust allergy, he is often seen holding a handkerchief in his left hand.
Cool-headed and charming, Soma usually appears to be calm, collected, and polite, carrying himself in a manner of a consummate professional. In contrast to his brutish subordinate Daimu Akutsu, Soma is much more reasonable and rarely loses his temper, the only notable exception when he lost to Yagami in the their second fight. Soma's former superior, Irie described that Soma always has a natural disposition to follow commands well, yet also possesses air of authority too. He displays a dry sense of humor and doesn't mind bantering with others, as demonstrated with first encounter with Takayuki Yagami and Masaharu Kaito or exchanging quips with Jin Kuwana.
He is also shown to be incredibly sharp and perceptive, being able to detect lies easily and deduce what someone is thinking just from a glance. Calculating and secretive, Soma approach situations in a swift and pragmatic fashion, especially in maintaining his status of an undercover agent. He purposely put Akutsu as the "public face" of RK, while he works behind-the-scenes and focus on strengthening the organization. Soma even bugged one of RK-owned cabaret clubs to keep an eye on Akutsu and quickly ordered his death after he found Soma's allegiance to the police. Whenever the presence of cops is near, Soma always choose to retreat and is adept in covering his tracks, all the while continuing to run RK from the shadows. Throughout his hunt for Kuwana and his conflict with Yagami Detective Agency, Soma also shown to favors sneak attacks and is not above fighting dirty, such as attempting to kill Kaito from behind or endangering teenagers to get to Yagami. During a parley with Yagami and his friends, Soma honored his deal with Kuwana not to harm the party, but cleverly prepared a realistic paint-ball gun to distract them and make his get-away.
Underneath his composed and affable demeanor, Soma is a merciless killer whose only interest is accomplishing his missions for Public Security. Soma has a sadistic streak, openly admitting that he enjoys work he does and relishes the murders he carries out, even having a weapon preference to use on his victims - a knife for males and an icepick for females. He has no qualms with killing innocents should they get in his way or pose a threat to his identity as an undercover agent for Public Security. With his deeds under Public Security's sanction, Soma believes his actions are completely justified, calling them a necessary evil and states it gives him a sense of "purpose". Soma outstates that everything he does to protect and upload order, not people, and is for the greater good of Japan, which only disgusted Yagami and remarked how "twisted" Soma is.
Soma was born in the year 1987. Except that he "hated [his] Japanese teacher" in high school, nothing is known of Soma's background before he joined the National Police Agency's Public Security Division, where he was trained as a spy. In 2009 at the latest, he was planted as an undercover agent in the Tojo Clan's Nikkyo Consortium under Hidemi Bando's orders.
He and his friends seduced women for large sums of money, which he spent at a Consortium-run underground casino in Kamurocho to draw the Consortium's attention. As planned, he was scouted by the Consortium's lieutenant and his apparent attachment to the lieutenant gave him an alibi for swearing himself in. Records of his identity were erased, and with nothing to link him to Public Security, his infiltration was a success.
He was derided and often beaten by his superiors for his dust allergy. However, his patriarch Irie recognized that his personality and ability to detect lies made for a natural yakuza. Soma was involved in several risky assignments during his time, including the kidnapping, murder, and remote burial of a police informant. He carried out the hit so efficiently that he was suspected of having prior experience.
He and Daimu Akutsu undertook off-the-record work, though their earnings were seized by their superiors. By all appearances, they were ambitious underdogs for most of their careers until they became officer candidates. However, once Public Security informed Soma of the Tojo Clan's impending disbandment, he left. Although he had no money and left without notifying his superiors, he was not pursued, which was unheard of at the time. Akutsu knew Soma's plans to leave beforehand and try to talk him out of it, but Soma laughed it off and advised that Akutsu should leave too.
While the Tojo continued to deteriorate, he founded RK in 2018 or 2019 with backing from Public Security. As he had been the first to leave the clan, he earned a reputation for being near-clairvoyant after its dissolution in 2019. To provide Public Security a means of continuing to monitor criminal activity in Kamurocho, he focused on inducting the ex-yakuza that remained in the area into his network.
Based on his own experiences, Soma devised several methods to appeal to younger ex-Tojo yakuza. The first was the name itself, RK (short for Red Knife, a reference to Soma's preferred murder weapon for men) was chosen as a Westernized name to distance the gang from yakuza traditionalism, which many had become disillusioned with after their treatment in lower ranks and the fall of the Tojo Clan. Another was the abolition of the strict hierarchies that prevented most from advancing their careers, to which Soma instituted a ranking system ascending from F rank to A rank instead and members of higher rank would be rewarded with better-paying assignments. While most started at F rank, ex-Tojo yakuza started at B or above, another measure designed to entice them to join.
With this structure in place, Soma invited Akutsu to join RK as an officer and act as the organization's public face, which Akutsu accepted. He also extended invitations to other junior members of the Nikkyo Consortium. By 2021, he and Akutsu established RK as Kamurocho's largest gang, with fifty full-time members and two thousand part-time members.
Despite Soma's efforts to set RK apart from the Tojo Clan on the surface, its regular operations, which included protection rackets, loan-sharking, and muggings, were typical of the yakuza. He took on the responsibility of educating members who were unfamiliar with these tasks, making RK fit to be described as "an unemployment agency for scumbags."
Lost Judgment: 2021-2022
In order to gain leverage over Reiko Kusumoto, Soma receives orders from Bando to search for Shinya Kawai, which he passes on to his subordinates. They discover it is very likely he was killed when he disappeared from Kamurocho five years prior and cannot find his corpse. He returns to RK's hideout and calls off the thugs sent after Takayuki Yagami and Masaharu Kaito, though he tells the duo they may cross paths again. They shift their attention to Yu Kitakata, who acts under the alias Jin Kuwana, leading RK to Isezaki Ijincho.
To lure Kuwana, Soma sets a trap for him by having his former student Yoko Sawa call him to her apartment. He waits in a car nearby and has his subordinates attack Kuwana and Yagami, who is also present. When the two leave, he has Sawa's locks torn down and holds her hostage over a video call to deter Yagami. Once Yagami is knocked unconscious, due to the crucial information Sawa is close to discovering, he jabs his ice pick into the base of her neck, killing her instantly. Bando ensures any camera footage showing RK members is wiped to prevent Soma's arrest. Soma interrogates the captured Yagami afterward, then orders him to be killed after it is discovered he is lacking the knowledge they need.
Because Kuwana was able to flee, his remote relative, the Siren Owner, is targeted. Soma arrives at Siren, but is unable to find its owner. He lies in wait, then calls the bar's phone to distract the recently-arrived Yagami and Kaito, mortally stabbing the latter when the opportunity presents itself. He fights Yagami and has him dazed when he is about to kill him, but the Siren Owner calls the bar's phone to let Soma know the police have been called to the area, prompting him to leave.
Soma orders Akutsu's death in Kamurocho after overhearing the latter learning of his true loyalty towards Public Security. Soma himself remains in Ijincho, issuing orders to RK, including an order to raid a gambling den that refused to pay fees. He receives an update from Bando where he is notified of Kuwana's connection several Kurokawa Academy alumni, one of them being Yasushi Akaike. Through secretly following Akaike, Soma finds Kuwana to a ship and kills Akaike by slitting his throat, then orders his lackeys to capture Yagami and Kuwana. However, Kuwana detonates a bomb on the ship, prompting Soma and the rest of RK to leave to avoid the imminent public gathering.
When the retrial of Akihiro Ehara soon underway, Soma orders RK members to kidnap Mami Koda and Akane to draw out Yagami and his allies. Despite a fight breaking out, Kuwana remotely negotiates with Soma for the lives of Yagami and co. in exchange for revealing the location of Kawai's preserved body. Soma arrives at the abandoned building RK had lured them to, and passes on a message to not mention Reiko Kusumoto's name during Ehara's retrial. When Yagami rushes to capture him, Soma shoots Akane with a paint gun to create a distraction so he can leave.
In 2022, the location of Kawai's corpse is revealed by tracing a call from Kuwana, causing all of RK to head to the location. After searching the farthest end of an underground warehouse, RK stumble upon the freezer containing Kawai, and Kuwana tries to kill Soma. Yagami then arrives, joined by Kaito, Sugiura, and Higashi. A fight breaks out, during which Soma lures Yagami to a cold storage unit for the purpose of killing him, but is defeated, choked out, and tied up. Soma is arrested when the police arrive, compromising Bando's scheme.
Quick, agile, and precise, Kazuki Soma wields a small pocket knife to kill and fight with whoever interferes with his work or is his target. He performs wide and quick slashes that causes the player to sometimes bleed. He also has access to a blocking-turned-parry stance where he blocks and when attacked from behind, will parry the player and follow up with a taunt and a new stance along with a temporary heat flare emitting around his body if not in his heat state yet. Once attacked in that current stance whether it be a low or high attack, Soma will retaliate with a slash either way although both stances are vulnerable to wall attacks and the Leapfrog skill move.
He will also sometimes lunge at the player when knocked down and will charge up an attack randomly. He also sometimes uses his legs during battle when he slashes and sweeps the player off of their feet.
During his Heat state, Soma emits a red/orange aura, and has access to two mortal attacks and will perform a new move randomly. He randomly and oddly walks backwards and teleports behind the player to stab them or grab them. This grab move can be dodged but if it was too late, Soma will either stab you which can take up a lot of health or grab you. His grab will cause a button to promptly pop up to escape his grasp but whether you don't escape or not, he'll release you but will take up a huge chunk of health.
- Ryu Ga Gotoku Studio. .BIN File — "character_model_model_data.bin". Lost Judgment. SEGA. PS4/PS5/XB1/XSX|S. 2021.