Hagun Academy
Stella Vermillion
Ikki's Fiancee/Roommate. The two started off with a rocky relationship due to Ikki accidentally seeing Stella changing and Ikki suddenly stripping to (unsuccessfully) even the situation. After their mock duel, Ikki and Stella start to become closer, becoming good friends and rivals. Despite being initially unaware of her feelings of affection towards him, Ikki admits to himself that he respects Stella as a knight and also finds her extremely attractive.
During Ikki's debut battle against Shizuya Kirihara, he nearly broke down due to mental stress and constant discouragement by the audience. At that moment Stella screamed encouragement towards him, suddenly confessed her feelings. This gave Ikki the motivation and courage to see through his opponent's attacks and easily overcome him. Sometime after his victory, Ikki woke up after collapsing from his injuries and fatigue and found out that Stella had stayed with him ever since, where he then confessed his feelings for her. Stella accepted his feelings along with a promise to battle him once the festival is over without losing to anyone else up to that point.
Ikki then goes to the pool to train Ayase, and as the day progressed, Ayase decides to push Stella and Ikki's relationship by leaving them alone together. After an awkward conversation, and yelling, Ikki and Stella then go to a more private place, where Ikki and Stella are finally able to solidify their relationship as they are able to kiss each other.
After his victory over Tohka Todo, Ikki proposed to Stella, to have a family with him, to which she accepted, much to his happiness. After which Ikki has started to be a little bit more courageous about his relationship with Stella grabbing her hand, in public, although he does get embarrassed when Stella responds with an even more affectionate act.
Ikki told Stella during the incident at Okutama that they shouldn't have a sexual relationship before meeting Stella's parents. However, he changed his mind after fighting Stella in the final match of Seven Stars Sword Art Festival because he didn’t want anyone else to have Stella and wanted all of her to himself only. In the infirmary where they were resting right after their match, they finally consummated their relationship. The next day they planned to go meet Stella's parents a week later in Vermillion, which Ikki reluctantly agreed especially after Stella noted he couldn't run away now that he had deflowered their nation's princess.
Ikki would meet Stella’s parents later on as well as her sister Lunaeyes. Stella walks in on him and her half-sister naked sister resulting in a shocking situation.
In Volume 18, after Ikki was transformed into a younge form following his near death experience, he would meet again with Stella in the women’s bath. Stella would scorn him for this, but would give him a bath with her breasts(which hit his head) and also say he looks cute. As they take a walk, they are ambushed by Abraham Carter who knocks out Stella and fights Ikki before his creator Carl Islands kidnaps her.
In Voluke 19, Ikki and his friends lead the effort to rescue his love. They destroy Carl’s body and free Stella from her bindings, she is revealed to be possessed by Islands. Islands/Stella explains how he destroyed her personality to turn her into the holy mother for his ultimate weapon. Ikki is heartbroken but chooses not to give up after Shizuku encourages him. Ikki fuses with Stella to undo the possession, and finds her inner self old and haggard from Island’s mindrape(Islands warped her memory by twisting a traumatic event). Ikki affirms to Stella that he loves her, and strikes the elderly inner Stella with his sword which causes her to be freed from the brainworm Islands implanted. Ikki, Stella and all their allies flee the Island as it is about to self destruct.
In the epilogue, Ikki and Stella get married with all their dearest loved ones in attendance. Stella also says she wants to have many kids
Kurono Shinguuji
Ikki's school director, she promised Ikki that if he would win the Seven Star Sword Art, she would make him be able to graduate even if he is Ranked F. Kurono was among the few who already knew how strong Ikki really was before everybody started taking notice of his true abilities. Nonetheless, she can't help but be impressed whenever he goes beyond her expectation. Such as not only surviving a battle with Edelweiss, the world's strongest swordsmen but even managing to injure her.
Yuuri Oreki
Ikki and Yuuri are on good terms with each other. Ikki is thankful to Yuuri for her unbiased view towards him during his entrance examination day. He also shows understanding of Yuuri, knowing that she was pushing herself so that the new students don't feel the tension.
Nagi Arisuin
Ikki and Nagi are shown to be on good terms with each other with Nagi serving as a sort of adviser to Ikki over certain issues.
Ayase Ayatsuji
Ikki's relationship with Ayase started out as just master and pupil, as she needed him to help her with her swordsmanship. This, however, grew into a friendship, as Ikki saw Ayase as a kind and sweet girl, who would always do the right thing. Ayase also seems to admire Ikki for his strength and courage always willing to fight for his friends.
Ayatsuji Dojo
Kaito Ayatsuji
Ikki has much respect and admiration for Kaito, as he was a swordsman who could take on blazers, with only his swordsmanship. Ikki saw him, and many other famous swordsmen, as a teacher. After Kaito woke up from his coma and heard about Ikki from his daughter, he called Ikki to have him marry Ayase and succeed his dojo, much to her embarrassment.
Tonrou Academy
Kuraudo Kurashiki
Ikki had the initial impression that Kuraudo was a horrible person who did not really care much for anything and showed a lack of respect for many people. This however changed into respect, as he saw Kuraudo as an honorable fighter, who did not even show weakness to his opponent, even when he was badly injured. The two admitted that they're somewhat similar to each other. Mainly because they both enjoy fighting strong opponents and respect swordsmen.
Kurogane Family
Ryouma Kurogane
Ryouma is Ikki's Great Grandfather and Ikki respects Ryouma a great deal and has looked up to him since he was a little kid. He was always pushed by Ryouma to become a knight, allowing Ikki to believe he could become such.
Itsuki Kurogane
Itsuki is Ikki's biological father and Ikki had never hated his father for anything he has done to him. He has always loved his father, no matter what the circumstances he had put him in, and even hoped that he could someday mend his relationship with his father soon.
He eventually met with Itsuki while he was in captivity and was very happy to see and speak with his father after ten years. He had however felt remorse for these feelings, after learning that Itsuki did not hate him but simply did not have any expectations of him, believing that he would never amount to anything, simply because it was futile. Also, he believes Ikki's successes will give false hope to the other low-ranks and bring about horrible outcomes that could destroy the harmony that the Ranking system maintains. He had cried once hearing the truth from Itsuki. He no longer sees him as a father nor neither considers it, after that interactions.
However, after learning of how Sara's relationship was with her father, Ikki came to realize that his views of his father were wrong as Itsuki had to been influenced by his own father. Therefore, Ikki rejects Itsuki's offer to cut off his connections to the Kurogane family as he acknowledges he will always be a member of the Kurogane Family and therefore Itsuki's son, which causes Itsuki to finally admit his son has become a big person.
Shizuku Kurogane
Ikki's little sister. Shizuku is the only family member that didn't discriminate against Ikki, thus the two have a close relationship. Shizuku, however, sees Ikki as more than a brother, a feeling that Ikki does not share and is admittedly disturbed by her actions that cross sibling affections.
ikki and Shizuku help each other out several times after the seven star sword festival, and participate in battles against the Rebellion. When Ikki nearly dies in Volume 18, Shizuku(by giving up some of her somatic cells) revives him which changes him into a younger form.
After Stella was kidnapped by Carl Islands for his goals of world domination, Shizuku accompanies her brother and his friends to rescue her.
Ouma Kurogane
Ouma is Ikki and Shizuku's older brother and seems to care very little for either of them, although Ikki still seems to think of Ouma as his older brother. When Ouma confronts Ikki before the tournament, it appears that he too discriminate against Ikki for being an F-rank knight like the other Kurogane Family as shown when he demands that Ikki withdraw from The Seven Stars Sword-Art Tournament as he believes that his strength is nothing more than a "deception" and that he is blocking Stella's progress. Ikki refuses, and Ouma tries to force him out by trying to kill him but is stopped by Yuudai. Ikki later tells Ouma how he admired him in his childhood, as he was always so dedicated and carried the expectations of everyone. After his defeat by Stella, Ouma realizes that Ikki was encouraging Stella progress and decides to fight Ikki in a duel to learn his strength, but the end result was never known.
Akatsuki
Amane Shinomiya
Ikki and Amane seemed to have a good relationship with each other as Amane seemed to admire Ikki and understood who Ikki was, someone working very hard to be the best. However ever since Ikki had met Amane he had this feeling in his gut that Amane is very dangerous and someone to not be trusted, even though Ikki has no reasonable reason to feel such a way.
Sara Bloodlily
Sara believes that Ikki is the perfect model that she has been looking for. Sara wishes to paint Ikki nude for her painting, which would finish it. Ikki however is hesitant towards the idea. Despite this, they are on fairly good terms, with Sara having told Ikki about her past.
Vermillion Empire
Sirius Vermillion
Sirius is Stella's father. He loves his daughter very much, he is against Ikki and Stella's engagement. As such he put a high bounty on Ikki's head. After the deal that if Ikki helps bring a win for Vermillion in the "war" then he and Stella can get married, Sirius tries to get rid of Ikki by challenging him in a number of tests. Ikki goes along with his tests to obtain his good grace.
Astrea Vermillion
Stella's mother, she is not as against Ikki as her husband was, but had to look at the political side. She was more or less avoiding talking to her husband after he would not at least give Ikki a chance after the proposal that Luna made to appeal to everyone.
Lunaeyes Vermillion
Stella's elder sister, she is not for or against the engagement. She seems to be friendly with Ikki. Luna suggested that Ikki prove himself to be good enough to marry Stella in the "war" and help Vermillion win.
Others
Edelweiss
Ikki and Edelweiss respect each other, being skilled swordsmen. After their first encounter, Edelweiss has opened up more to Ikki, telling him about her past and even training him. Ikki also greatly admires Edelweiss' swordsmanship.
Yuudai Moroboshi
Ikki and Yuudai have a friendly relationship, both respecting each other's abilities. Yuudai and Ikki are also fairly similar, both being very tactical fighters. Yuudai is also thankful to Ikki, for having helped in the recovery of his sister's ability to speak.
Iris Ascarid
Though they only knew each other for a short time, Ikki and Iris had a great deal of respect for one another. Even after Iris betrayed their side to save her evil younger brother, Ikki didn't think badly of her because he understood it was her own justice (chivalry). She was deeply thankful to for staying and decided to show her full respect by fighting her with everything he had. In the end, Ikki manages to defeat her but still felt painful because he saw her as a friend and considers her a kind person for wanting to save her only family member.