Kurogane Family[]
Ikki Kurogane[]
Itsuki and Ikki's relationship is very strained, as Itsuki thinks nothing of his son, but a failure, as he was only an F-Ranked Knight, due to the lack of his magical power. Itsuki has given up Ikki as his son, and tries very hard to make sure he and Ikki are in no way linked together, going as far as to actually make Ikki fail his first year of Hagun Academy, using his power as one of the members of the esteemed Kurogane family, by not allowing him to take the classes he needed. He had completely broken off all communications with his son, for ten years, and the last thing he had said to his son, before his complete silence toward him, was that he should give up, and stop trying to be a knight.
As Ikki strived to participate in the Seven Stars Sword Art Festival, Itsuki saw his son as an obstacle to his own goals. Thus, Itsuki allowed Mamoru Akaza to use any sordid method in order to prevent Ikki from becoming a knight and did not care if Ikki ultimately dies because of Mamoru’s methods.
Itsuki had eventually talked with his son, ten years later, and had confirmed that he did not hate Ikki, he only did not have any expectations of him, and there for would rather him accept that he would never be able to become anything, it was a futile effort as he could not do anything. 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.
Later, Itsuki proposed that Ikki would break ties with the Kurogane Family, which would be beneficial to both of them. Ikki, however, denied Itsuki's proposition, admitting that no matter what, he is still part of the Kurogane Family. Hearing Ikki's words, Itsuki admits that he has become a big person.
Genma Kurogane[]
Genma was the father of Itsuki. Genma was a strict person, who held the traditions of Kurogane in a high regard. Genma raised Itsuki with these ideologies, which shaped Itsuki into the strict person he is now.
Shizuku Kurogane[]
Itsuki seems to care a great deal about Shizuku, as he had spoiled her as a child never having punished for anything. However, Shizuku grew to hate her Father for his horrible actions and coldness towards her Brother.
Ouma Kurogane[]
Eldest son. Ouma seems to take requests from him, even after abandoning the family.
Ryoma Kurogane[]
Ryoma is Itsuki's grand father, though their exact relationship is unknown.
Others[]
Bakuga Tsukikage[]
Itsuki seems to agree with Tsukikage's idea of Japan splitting from the League of Mage-Knight Nations, as it would bring more power to the Kurogane Family. Itsuki even asked Ouma to join Akatsuki.
Sirius Vermillion (Anime exclusive)[]
As news of Ikki's victory reached his country, Lord Vermillion expressed his discomfort to Itsuki's reprobate involvement and told Itsuki to "not get our kids involved in adults' schemes."