Koukin is Hakufu's cousin and housemate. They are rather close with each other. Koukin often tries to save her from doing foolish antics as well as shielding her breasts when they are bouncing or exposed for people ogle at. Koukin and Hakufu do however argue constantly because of the former's cautiousness compared to the latter's recklessness. Hakufu notes that Koukin has seen her in the buff many times that she is only embarrassed when others are similarly seen. Overall, Koukin loves Hakufu and wishes to keep her safe even if it costs his own life. However Hakufu deeply cares about Koukin and also depends on him to carry her on his back whenever she is hurt, tired or sleepy.
She never had sex with Koukin the only reason she was in the same bed was to keep him warm after he saved her from the Dragon spreading in her body but he feels love towards her while Sonsasku has not responded because she doesn't know his feelings yet.
Although initially foes, the two become friends through working together in the Big Fighters Tournament. Gakushuu is seen alongside Hakufu after she becomes Nanyo's leader. He even took a dive for Bachou Mouki on Hakufu's say so.
Initially a rival at the school that Hakufu attends, she at first tries to kill Hakufu, however, the order is withdrawn when she learns of her cluelessness. At the hot springs she grows closer to Hakufu and the two become friends. Hakufu likes to act casually around her, groping her on occasion.
Goei is Hakufu's mother. She often tells Koukin to look after or check up on her daughter. Whenever Hakufu acts up or insults her, Goei responds by spanking her. However she deeply loves Hakufu and entrust her daughter's safety to Koukin. Also initially she was against Hakufu and Koukin having a romantic relationship, but later she is shown encouraging it by asking Koukin to sleep with Hakufu much to his surprise.
Hakufu has a positive relationship with her false sister.