Bukyoku Academy[]
Yuudai Moroboshi[]
Byakuya and Yuudai are close friends with one another being on the same team and school as one another. He lets Yuudai even refer to him as "Shiro" due to the characters in his name, as well as being able to respect yet be somewhat afraid fo him in a fight.
Momiji Asagi[]
Byakuya is close friends with Momiji, while he also having romantic feelings for her, but it is unknown whether or not she is aware of this.
Hagun Academy[]
Ikki Kurogane[]
As his upcoming opponent during the 62nd Seven Stars Sword Art Festival, Byakuya has studied him a number of times and even diving into his background in the Kurogane Household. He is also seen to have a great deal of respect toward due to their similar perceptive skills even holding Ikki in high regards even after being defeated in the record-shattering time by him after using both Ittou Rasetsu and Edelweiss' Swordsmanship.