Hanabi has a grandmother. She frequently contacts her. In an extra chapter, it's revealed before she asks Nozomi to exchange email, her grandmother is the only one contact she has in her phone.
During the training camp, Shirayuki is in charge of coaching the Infighters, this includes Hanabi. After Hanabi officially becomes a Keijo player, Shirayuki becomes Hanabi's mentor. Hanabi starts to address her as "Onee-sama". In turn, Shirayuki calls her by her first name, "Hanabi".
Hanabi is Nozomi's last opponent on the final exam. Nozomi praises Hanabi upon knowing that Hanabi is capable of targeting any weak spots in the human body. In turn, Hanabi respects Nozomi greatly. Since Hanabi is too talented in sports, her friends are irritated, but Nozomi is the first to be able to rival her. Thus, thanks to Nozomi, Hanabi is finally able to enjoy sports for the first time.
Rin is Hanabi's roommate. Hanabi calls her "Rinrin". In turn, Rin calls her by her last name, "Kawai". The two are on the same team when they participate in the eleventh East-West War. When Rin is cornered by the opponents, Hanabi is willing to protect Rin. Despite this, Rin is sometimes bothered when Hanabi over talks about boys.