Boris Ivanov is a member of Yomi, practitioner of Combat Sambo, a soldier for the Russian Armed Forces, and the former disciple of Alexander Gaidar. He is the second Yomi member to fight Kenichi in a duel (the first was Ryūto Asamiya, though it was before he joined Yomi) and is one of the first four Yomi members transferred to Kenichi's school. He was awaiting his former master's return, but is currently a participant in the Eternal Sunset, along with the other members of Yami and Yomi.
Boris is usually seen in a grayish camouflaged military outfit due to his loyalty to his country and has a muscular build. When wearing this outfit he covers the sides of his face with warpaint to symbolize himself as a soldier. His hair is silver and spiked in the back and usually has a small headband around his forehead. He was seen in a school uniform to fit in at Kenichi's school.
Being a Russian soldier and the right hand man to a colonel, Boris frequently acts in a militaristic manner. He strictly upholds orders and believes orders are absolute, as he will follow any order from his master or his teacher without question or hesitation. He also particularly hates anyone who disobeys orders, and seems jealous when he finds someone with greater loyalty than his. He seems to have a small degree of respect for anyone who is willing to speak against him openly. Although he is an enemy of Kenichi, he will work with him to take down some opponents and find ways to listen to him, such as hearing Kenichi's words as advice and tips, not orders. He will also find loop holes to turn orders to his advantage without going against them.
Like Ethan, he was one of the few YOMI students to actually leave a good impression on most of the students their and held a respect for his teacher, Kyōko Ono, doing anything she asked without question and always did good deeds at his school. The teacher always thought of Boris as a very kind person, which may not be an overestimation, as he did ally with Kenichi to keep her safe from his own men due to loop holes he found, suggesting he may not be as bad as he seems and actually be more lenient towards the saving fist. He gets along well with his militia men as they follow him as soldiers and commander but doesn't seem to listen to Sho until he hears his master's orders first. Boris is also the first opponent to acknowledge Kenichi for his strength, even to the point of even conceding that he is stronger.
Boris is very good at intelligence gathering, having been able to find Big Lock all on his own, a very impressive feat as even master class fighters are unable to find the prison.
- Skilled Soldier - Boris has been trained as a martial artist, but also as a soldier as well. Because of this, Boris has developed a unique sense of battle, being able to dominate multiple opponents as if he was on a battlefield. This has also allowed him the ability to combine his training as a soldier, with the skills and techniques he received from his master, giving him a very rigid, but powerful battle style. As a soldier, he has been trained to be prepared for death, this resolve has been farther strengthened by his master's training and as such, he is completely prepared to give up his life for victory at all costs. This was shown during his invasion of Ryōzanpaku, when he took a blast of Sakaki's Ki and was able to stay standing, despite being greatly effected by the strength of it, and it was also shown during his second fight with Kenichi, when he gladly told him that he was ready to die in order to defeat him.
- Enhanced Speed - Boris is a very fast individual and uses quick and fast choke holds and spins. Even in the water he's very fast and a strong swimmer, capable of winning the school swimming contest on the camping trip and keep Kenichi on the defense while in the water.
- Enhanced Strength - Boris is a strong fighter and the offensive style of SAMBO compliments Boris's powerful strength and most of his attacks relies on his strength. He's strong enough to even injure Miu, a very talented fighter with a punch to the side.
- Strength Analysis - Boris is able to look into an opponent, primarily through its killing intent, and compares it to an animal of sorts. When he first saw Kenichi, he saw him as a "fangless, clawless, small creature that was taunting him", visualizing it as a penguin, throwing his guard off for a brief moment and confusing him. The second time they fought, he realizes that "the little creature" had evolved into a truly fierce beast, as he visualizes a emperor penguin.
- Intelligence Gathering - Boris's greatest feat lies in his intelligence gathering. As in no less than a year after his master's defeat and arrest to Big Lock, Boris was able to track him down and find the prison greeting him and Diego when they "went on a walk" away from the prison. Both Diego and Alexander praised his skills in intelligence gathering.
Boris's past from before joining Yomi is largely unknown. The only known things about his past is that he joined the russian military roughly around the same time he became Alexander Gaidar's disciple, and when Gaidar joined Yami, Boris joined alongside his master, joining Yomi in the process, everything outside of those facts remains unknown. It is also unknown if Boris was aware of, or even involved in the any of the alleged crimes that his master committed during his time in the russian military, but it can be greatly assumed that if he was involved in any way, he would of been ordered by his master to stay quiet about these events.
Boris is first seen arriving in Japan illegally to meet Sho. Not long after, he and some other Yomi members went to challenge dojos. Unlike the rest of his fellow Yomi members, however, Boris was unable to receive calls from his teammates and tried to take down all 58 dojos on his list (59 including Ryozanpaku secretly put on by Ogata). Upon entering, his men were quickly taken out by the traps Shigure installed to catch Kenichi and he tried to confront the Ryozanpaku masters, who were worried because they didn't have a disciple to fight him. Upon spotting Kenichi's entrance, Boris attempted to attack Kenichi but was forced to take out Miu, who was defending Kenichi, with his combo attacks. This unknowingly caused Kenichi to fight seriously. Boris became confused about Kenichi's power and heart, as his analysis revealed Kenichi as nothing more than a normal person. Sho called and told him to retreat, ending their match. Before he leaves, Boris gives Kenichi his Yomi badge stating a challenge. His disobedience of Sho's orders places him under house arrest. He is visited by Radin, who takes an interest in Kenichi after hearing about the strange light in his eyes.
Following Sho's defeat and death, Boris, the Stanley twins, and Tirawit transfer to Kenichi's school. Boris acknowledged his teacher, Kyōko Ono, as his stand-in commander. During this period, he seemed to ignore Kenichi and follow the teacher's orders. A little while later, he met his master back at Russia and he told him that he was elected class representative. The next morning he arrived back at Japan by plane, happened to land near Kenichi, and quickly ate breakfast. Later at night, he met up with his master to try and assassinate a congress woman containing information about Yami. Boris met Kenichi and mentioned that Kenichi evolved from a harmless animal into a dangerous threat, desiring to fight Kenichi but maintains the order to hold off Akisame until Kenichi intercepted him. He and Kenichi make it to the top of the building structure and witness their masters fighting each other. Kenichi's endeavor to rescue the congresswomen prompts Alexander to order him to take the congresswoman to the chopper. He failed and later witnessed Kenichi save the congresswoman. After he and his master retreat he started to question his loyalty to his master compared to Kenichi's loyalty to his, and that this was his most humiliating defeat.
Boris keeps a low profile in school throughout the next few days, even at the school festival. Kenichi's return after being defeated by Tirawit prompts Boris to mention that Kenichi's eyes didn't show the eyes of a deceased martial artist and wonder if Tirawit miscalculated. Later when his teacher mentioned the camping trip, he saw this as the perfect opportunity to finish off Kenichi and that all he needed was the order from his master.
Boris plans his attack on Kenichi during the trip. He develops a close relationship with Ono, but attacked on instinct when she brought him food, prompting her to express concern about Boris taking things too seriously, which made Boris doubt himself. Commencing the attack, he immediately fought Kenichi but postponed the fight because he wanted to stop the attack on the innocent but couldn't reach his master and has lost control over his soldiers. When the soldiers refuse to stop, Kenichi asks whether this was treachery against orders which Boris agrees to, stating that the soldiers were performing acts "of disobedience' and a 'staged revolt' and attacks the troops with Kenichi as a team. After saving their teacher, Boris and Kenichi continue their battle. Ono awakes momentarily to see them, and smiles to herself thinking "Boris has finally found a friend" (mistaking their fighting in a river as playing in the river). Boris states that in all of Kenichi's previous battles, only Kenichi fought so as not to die, and that none of his enemies fought as such, but in this battle, Boris was also fighting not to die. Kenichi manages to gain the upper hand by countering all of Boris's attacks, forcing Boris to use his Forward March of Death to finish off Kenichi, concurrent with Alexander using the same move against Akisame, betting on whose belief was stronger. Kenichi then countered him with the Shimewasa to knock him out.
Upon waking up, he realized that Kenichi had won after knocking him out for about a minute. He receives a message from his master telling him to erase all relationships with Yami and their relationship as master and disciple. Receiving this last order, he said his master had disowned him before telling him to not search for him, thereby allowing him to ignore the second order and was free to go search for him. Boris reappears after disappearing for a little while and apologizes for his soldiers' rude behavior. Boris then tells Kenichi that all he did was to go change his clothes and to follow his teacher's final order to behave like a normal student and have fun. After Ono defends them and covered up their fight, he had fun with the other students, much to their surprise. Before he leaves, he tells two students to continue defending the instructor while he's gone, commending them for being able to stand up to him, and polishes all of the school windows in a single night as a farewell gift, leaving Ono crying tears of sadness (for him leaving) but also of joy (for his last good act as a student of the school). His influence stays with the two students, as they uphold his instructions and tell off two other students who are talking during class.
After searching for a while, Boris finally found the Big Lock prison and was waiting for his master while he and Diego went "on a walk" to which he immediately asked his master to give him an order. Afterwards, his master and Diego went back inside while Boris awaited his return.
Much later, Boris is seen reunited with his fellow Yomi members (minus Sho and Jihan), as he prepares to fight the armed Yomi members, but are stopped at by Kajima who tells them to save it for the enemy. He was later seen gathered with all the Yomi members being lead by Kajima for battle. He was later seen with the rest of YOMI (minus Kajima) facing the Shinpaku Alliance. After Kenichi, Miu and Niijima escape, he and the other disciples charge the Shinpaku Alliance.
However, Boris and the other unarmed YOMI disciples remain on the sidelines during the ensuring battle. After Chikage's assault on the armed division's lack of honor and ganging up on the Shinpaku Alliance, Boris allies with the alliance temporarily.
Once they start to overwhelm the weapons team Hyougo starts to have them work together more effectively. Just then, two masters: Chin Sougaku (crescent moon spade) and Ortal Sin (jamadhar) arrive and begin to put pressure on them. However, Ryuto, Renka, Koan Shokatsu and Genson Ryu, Renka's fellow disciples, also arrive and attack the enemy reinforcements. Once Ryuto tells them what to do, Boris fights along side his YOMI disciples against Chin.
They all defeat the masters as the armed forces retreat, then celebrate their victory.
In the Epilogue Boris returns to his home country to run a commanding position by his master. He has also received an award for his efforts against Yami, much to his satisfaction.
- vs. 58 Dojo (won)
- vs. Miu (interrupted, Miu protected by Kenichi)
- vs. Kenichi Round 1 (interrupted by phone call)
- vs. Kenichi Round 2 (unfinished)
- vs. Kenichi Round 3 (loss)
- with Shirahama Kenichi vs. Russian soldiers (won)
- with Shirahama Kenichi vs. Lt. Girgins (won)
- with Yomi and Shinpaku Alliance vs. Yomi Weapon Division (won)
- Boris's main choice of words he says in almost every chapter he's in is "orders are absolute!".
- He's the first Yomi member to be transferred out of Kenichi's school from a loss. Kokin was officially the first to go but he wasn't defeated and only left due to the incident with trying to kill Kenichi.
- Curiously, the man that give an award to Boris in the Epilogue chapter resembles Vladimir Putin.