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 confessing 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'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.
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 towards Yuuri, knowing that she was pushing herself so that the new students don't feel tension.
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.
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.
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.
Ikki had the intial 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.
Ryoma is Ikki's Great Grandfather and Ikki respects Ryoma a great deal, and has looked up to him since he was a little kid. He was always pushed by Ryoma to become a knight, allowing Ikki to believe he could become such.
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 some day 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 see's him as a father after that interactions.
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 crosses sibling affections.
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 demand that Ikki withdraw from The Seven Stars Sword-Art Tournament as he believes that his strength is nothing more than an "deception" and that he is blocking Stella's progress. Ikki later tells Ouma how he admired him in his childhood, as he was always so dedicated and carried the expectations of everyone.
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.
Ikki and Sara have a friendly relationship.
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 challenge him in a number of tests. Ikki goes along with his tests to obtain his good grace.
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.
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.
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.
Ikki and Yudai have a friendly relationship, both respecting each others abilities. Yudai and Ikki are also fairly similar, both being very tactical fighters. Yudai is also thankful to Ikki, for having helped in the recovery of his sister's ability to speak.