Kiku is Hana's older sister, though the two were born in the same year. Hana has noticeable feelings of inferiority towards Kiku and tends to get envious when Kiku is given preference. She used to have more positive feelings towards Kiku, but this changed after Masao, a man she liked, asked Hana if Kiku was seeing anyone. Hana was very disappointed and her feelings towards the both of them turned sour. 
After Hana moved to Tokyo, she did not talk to Kiku for a while. After Hana meets her again, she makes it clear that she does not care about her anymore. As she interacts with Kiku, she tends to be boastful towards her in attempts to make Kiku envious. However, with more interaction between the two, her negative feelings disappear and she gains respect for Kiku. After Kiku leads the Sui-Sou Detective Team to confront Ageha's father, Hana tells Kiku how inspired she was by this. 
Hana would later tell Kiku that she is allowing Kiku to ask her for company now. In response, Kiku tells Hana that she'll protect her. 
Souseiseki is Hana's Rozen Maiden. She discovers Souseiseki's case after a ride in the elevator, deciding to take it with her back home.  Hana's initial reaction to Souseiseki is of adoration, commenting on how handsome and prince-like she is. She becomes very protective of Souseiseki when the young master shows up after Souseiseki is wound up and he demands that she pick him to make a contract with. Later that day she and Souseiseki form a contract. 
The two are shown adjusting to living together fairly quickly, though Hana occasionally finds Souseiseki hard to deal with. As Hana has taken up detective duties in addition to her job, it seems that Souseiseki has taken up some of the chores in their living space to ease Hana's workload, as she mentions doing Hana's laundry. It's also mentioned several times that when night comes Souseiseki makes Hana a cup of tea.   She carries Souseiseki in a bag most of the time, but once tried to hold her in her arms pretending to be a ventriloquist saying that they had practiced this. 
Hana blushes a lot in response to Souseiseki, which likely stems from a romantic attraction to her. She calls Souseiseki "prince" several times and also mentions that Souseiseki looks like "the foreign prince of my dreams".  When the two have a disagreement Souseiseki gets Hana so flustered that she begrudgingly gives in to Souseiseki's desire.  When the outcome of this event goes wrong, Hana tells her that she forgives her and Souseiseki apologizes. Hana reacts in surprise with hearts drawn around her.  She later receives a rose from Souseiseki while in the Miniature Garden.  After Kiku shouts from the top of the Youunkaku, Hana also shouts, exclaiming her love for Souseiseki. 
She is seen arriving to Souseiseki's aid in the N-Field after Suiseiseki falls apart. Hana is quick to notice Souseiseki's tears, and she comforts Souseiseki after the doll asks her for guidance. Later, Souseiseki begins to sing to unison with Suiseiseki's song. Hana takes interest in her singing and is the first to join her in song. They are seen holding hands singing together as everyone else joins in. In their final scene, Souseiseki apologizes to Hana for being late to the group's tea party.