When she is first introduced, Haruna is shown to have long, slightly unkempt black hair that extends down to her waist. She also has a blank yet manic smile on her face, likely caused by Saika driving her insane. In her first appearance, she wore her school uniform, which was similar in design to Raira's save for the much longer skirt and yellow tie. When she returns in volume 8, Haruna's appearance has changed significantly. Instead of her school uniform, she wears a long pink dress and a pink headband. She carries several small knives hidden under her skirt and uses a large red scythe instead of her old kitchen knife. Haruna also has several bandages wrapped around the spot on her neck where Anri cut her the first time they fought.
It is made very clear that Haruna was driven half-mad by Saika's influence and has deluded herself into believing she has control over the demon blade, when in reality it is the other way around. Under the influence of a daughter blade of Saika, Haruna fell in "love" with her teacher, Nasujima. She was caught trying to injure Nasujima with Saika's daughter and afterward had to transfer to another high school in West Ikebukuro. As of volume 8, while she still holds an unhealthy obsession with Nasujima, her mental state seems to be more stable than it was when she was first introduced.
At some point before the start of the series, Haruna entered into a romantic relationship with her teacher, Takashi Nasujima. While Nasujima was merely using Haruna to extort money off of her, Haruna was genuinely in love and grew obsessed with him. Eventually, Haruna came into contact with one of Saika's daughter blades and was eventually driven half mad by its influence. This resulted in her attacking Nasujima which caused her to get transferred to a different school in West Ikebukuro. As Saika's influence grew stronger within her, Haruna eventually decided to spread Saika's "love" across the city. She also realized that Nasujima had started make advances towards Anri and, out of jealousy, has decided to kill her.
Dollars/Mika Harima ArcEdit
In the anime, Haruna is on her computer when her father comes home.
Haruna starts the slasher attacks by cutting various people to "infect" others with Saika's spirit, making them her children. Haruna also runs into Shizuo Heiwajima at some point during her cutting spree and, seeing him as a useful tool, Saika compels Haruna to somehow bring Shizuo under her influence. A couple months into her plan, Haruna saves Anri from some bullies and runs off. Haruna is also seen spamming the chat room under the screen name of Saika. The others try to ignore her until she brings up Shizuo before abruptly cutting off communication.
Haruna decides to cut her father in order to use him as a scapegoat to attack Anri. When he fails to do so she decides to take care of Anri herself and pays a visit to her apartment. At the same time, Haruna also launches a full scale invasion of the city and sends her children to attack Shizuo. Haruna talks to Anri about Takashi and explains how she wishes to take revenge on Anri for taking him away. She then goes on to cruelly taunt Anri about the death of her parents. However, someone knocks on the door and Haruna goes to answer with the intent of cutting whoever was knocking. Much to her surprise, Nasujima was the one who was knocking, which causes her to chase after him while she leaves her children to finish off Anri.
She corners Takashi and rubs blood on his face in an attempt to show her "love." Anri then appears unscathed, much to Haruna's surprise. Haruna asks Anri how she survived and Anri tells her that she has the true Saika blade as well as how she obtained it, pulling out her katana as proof. Haruna insists that she has the true blade and attacks Anri several times. However, it is revealed that Anri is merely letting Haruna cut her as punishment for what she was about to do. She then cuts Haruna neck, taking control of Haruna, as well as all of her children. Haruna promptly passes out after hearing Saika's voice and asking Anri how she manages to cope with it.
At some point after her fight with Anri, Haruna manages to break free of Saika's control again and decides to take revenge on her.
She along with several others are called in by Izaya to work for him.
Dragon Zombie ArcEdit
She assists in rescuing Izaya after he got kidnapped by taking control of several members of the group "Amphisbaena" that were holding him captive. Izaya compliments her for using Saika instead of simply suppressing it, but he narrowly avoids her attack. Haruna asks if Izaya will keep his word about leading her to both Anri and Takashi. Izaya reassures her and requests that Haruna take control of Earthworm (the leader of Amphisbaena) so that they can use her.
Kadota's Coma ArcEdit
There are several scenes of Shuuji Niekawa looking for his runaway daughter, by approaching the police as well as the Awakusu, which eventually end in him meeting Mikado Ryuugamine and the Blue Squares. Shuuji Niekawa says, apologetically, that when he looked through her computer to find clues as to where to find her, he found that she was involved in the Dollars.
Under Orihara Izaya, Haruna sends her "children" to attack Jinnai Yodogiri. The police officers in custody of Shizuo are her "children" as well. It is almost certain, although never stated, that Izaya had her cause Kadota's accident. Kadota is not seen conscious after the accident so it is unknown if he saw the culprit.
Saving Izaya/Haruna Returns ArcEdit
Anri bumps into Haruna who asks her to follow her to a park. Anri asks Haruna if she’s planning on killing her. Haruna said that she would if she were younger but will forgive her now and asks to collaborate but Anri rejects her offer. Haruna thanks her for rejecting her because now she has a reason to fight her, but as they begin to fight they are interrupted by Kasane Kujiragi, and Haruna is quickly subdued by her with an electric shock. Once she recovers, she tags along with Kasane and Anri to discuss Saika civilly in a cafe. After their talk, Haruna leaves and is approached by her father. She initially dismisses him but is then attacked by him, who had been under the influence of Takashi's Saika.
Final Curtain ArcEdit
She and Takashi lead a group of slashers to try and break into Russian Sushi where Tom Tanaka is at. She plays along with Takashi's wishes, despite breaking free from his Saika, until his Saika army is subdued from Celty's shadows. Shortly after he attacks Mikado, she intervenes and chases him down. Once she succeeds in capturing Takashi, she brings him to one of Izaya's hideouts and sends a message to her father, letting him know that she is alright and that she is with the man she loves.