Erika has brown eyes and brown hair. Her hair is typically kept pulled back into a braid along the back of her head, with two pieces of her hair hanging freely in front of her ears. She normally wears a black newsboy cap and a long-sleeved, black cheongsam with black ankle boots. Erika is also seen carrying a small, silver slash bag.
Erika is a hardcore anime otaku, becoming extremely enthusiastic about anything anime or manga related. Her personality can come off as being hyper and strange, but she proves in episode 20 that she can be calm and can reason with people, although she goes right back to being her normal otaku self immediately after the topic changes. In the manga, Masaomi explains to Mikado that she and Walker are a bit peculiar, but good people. Like Izaya, she calls Kadota "Dotachin" as a playful nickname. She is a member of the anonymous online gang called Dollars; her friends Kadota, Saburo, and Walker are as well, which is one of the reasons why she is often traveling with them. Erika is shown to be a yaoi fan; whenever she sees Izaya and Shizuo fighting, Erika is convinced that the two are lovers, despite (or because of) their constant fighting.
Erika and Walker have darker sides of their personalities as they have been seen to be skilled in both mental and physical torture, displayed whenever the two need to extract information from someone. During interrogation, the torture they conduct is usually based on themes from a manga or anime series of the victim's choosing. Both Erika and Walker share the mentality that they were twisted from birth and that their affinity for torture would persist even if Anime didn't exist. Despite her sadistic tendencies, Erika still values her friends and companions deeply and will do whatever she can to protect them.
Very little is known about Erika and Walker's background before the start of the series. It is implied by Kyouhei that he met them when they were still involved with other criminal organizations and acted as interrogators. Kyouhei somehow managed to turn them away from a life of crime and helped them (mostly) re-adapt back into normal society. The two of them developed such a strong connection to Kyouhei that they were ready to quit the Blue Squares in a moment's notice when Kyouhei grew sick of the group despite the risk of retaliation. Not long after, they followed Kyouhei in joining the Dollars.
Dollars/Mika Harima ArcEdit
She and Walker meet Mikado and they tell him about the large stack of manga they bought. A couple days later she and Walker meet up with Kyouhei who was putting tiles on a bathroom wall. Erika suggests to eat at Russia Sushi. As they leave, Kyouhei gets a text from Kazutano, saying that he broke a plate. Erika wonders if Kazutano messed up his kanji and meant to say he'd been kidnapped, but the group found this unlikely and ignored the message.
After eating at Russia Sushi she and the others go to Kazutano's apartment to find the place is a wreck. Saburo deduces that he was kidnapped, to everyone's distress. After spending some time searching for Kazutano, Erika suggests calling him. Kyouhei does so, but hears Izaya on the other end informing them of the location of one of the kidnappers.
They go to the place to find Kanazawa sleeping. Erika and Walker suggest using manga torture to wake him up, but Kyouhei refuses on the grounds that they might accidentally kill him. Once Kyouhei manages to trick the other kidnappers into revealing their location, Erika is seen celebrating with the rest of her group. Shortly after being tracked down, the kidnappers leave Kazutano and run away from the Black Rider. Erika jumps back in the van with Kazutano and the others and chase them down. Morita gets away but they manage to corner Asanuma. In the morning, since the kidnapper refuses to talk, Walker and Erika tell Saburo that they can take care of him.
Saburo gets out of the van, telling them not to use gasoline again. In the back of the van, Erika and Walker pull out several manga books and tell the kidnapper to choose one. The kidnapper, becoming increasingly disturbed at the nature of the different books he sees, finally picks Black Butler on a whim. Erika hands Walker a mirror from her purse, which Walker breaks. Erika holds Asanuma down as Walker moves to the place the mirror shards in Asanuma's eye, but Kyouhei stops them once the kidnapper agrees to talk.
The next day she is looking around town wanting to give Walker's phone back to him after he left it in a maid cafe. She asks Simon in the park, but he says he has not seen Walker. Shiri walks up, telling her to sign her book that is labeled "Missing Stuff." She leaves Walker a message telling him to find her at Toranoana cafe. That evening, Walker finds her and the two dance.
A day later, she is with Saburo, Kyouhei, and Walker outside of Yagiri Pharmaceuticals when a passing van accidentally flicks a pebble at Saburo's car, scratching it. Saburo drives full speed at the guy but stops just in time to avoid running over Mika Harima. They sit with her, and as Mika explains her situation to them, they get a text to participate in the Dollar's meeting. Erika and the others attend the gathering, viewing the proceedings from inside the van, and marvel at how large the Dollars has become. While everyone else showed fear and confusion, Erika and Walker were excited when the Black Rider rode down the side of a building.
Erika and the others were driving around town at night with Erika teasing Walker about the book he was reading. Kyouhei asks why Walker was getting so worked up and critical, and she explains that it is because the book was something Walker himself had self-published. Kyouhei then tells them to focus on finding the slasher.
Erika is with the others as they save Anri from one of the supposed "slashers." Saburo hits Shuuji Niekawa with his van, but he simply gets back up and tries to attack Anri again. Suddenly Shizuo and Celty intervene and incapacitate him by crushing him with Saburo's van door (much to his distress). When Shizuo gets bored and leaves, mentioning his intent to kill Izaya, Erika gets excited, saying that Shizuo likes Izaya, which everyone immediately and fearfully denies.
The next day, after interrogating him, they release Shuuji, as he claims to not remember anything.
Yellow Scarves ArcEdit
It is revealed that Erika was a part of Kyouhei's crew when they were still part of the Blue Squares. However, they betray the group by saving Saki from Izumii and the gang's other higher-ups. Masaomi meets the group in the city and tells them that he needs to talk to them, taking them to a private room in Russia Sushi.
Masaomi asks them about the Blue Squares, but she and Walker do not give him any straight answers, pointing out Masaomi's temper and mistakes alongside the group's own. As the talking gets more intense, she and the others are startled when Denis throws a knife into the room, sticking it into the wall, telling them that their talk is scaring the customers. Outside, she fantasizes that Denis is a former Soviet spy.
Not long after, Erika and Walker are left out in the war between the Dollars and Yellow Scarves, as according to Kyouhei, they would "stand out too much." They take Masaomi to the hospital and are later seen sleeping in his hospital room.
Mikado and Anri turn to Erika and Walker for help in regards to giving Aoba a tour of Ikebukuro since neither of them are very good at showing people around. Erika and Walker try to give them some good tips and even make a list of what they consider some of the more interesting sites around the city but decide that it would be simpler to just come with them. After singing anime-themed karaoke for a couple hours, the four of them part. The next day, Erika, Walker, and Kyouhei save Mairu and Kururi from some Toramaru members and call in Saburo to pick them up.
The six are chased by Toramaru and eventually pick up Mikado, Anri, and Aoba as well. After meeting with Celty along the way, Celty relays her plan to Kyouhei to hold off the bikers until the van group can get the high schoolers to safety. Saburo drops the teenagers off at a police station, and Walker and Erika have to forcefully eject Mikado from the van, as he wants to stay with the other Dollars members. In the anime, Walker and Erika are left behind with the high schoolers. When the group arrives back under the overpass, they join Celty in watching as Ruri and Egor incapacitate the Toramaru members that were chasing them.
Several days after the incident, Erika, along with Celty, Emilia, Anri, and Mika, assist in the cooking for a hotpot party at Celty and Shinra's apartment. The color illustrations in the fourth light novel rate the girls' cooking skills, with Erika scoring an even 70 out of 100, claiming she can easily make anime-themed dishes.
Erika and the others are hanging out but Kyouhei notices Chikage following them. Erika's presence in the group is the only thing keeping Chikage from acting (due to his "no harming women" policy) and Kyouhei tells her and the others to separate.
Dollars and Blue Squares ArcEdit
Near the end of Kyohei's and Chikage's fight, Erika, Walker, Saburo and several other Dollars members show up to give them a helping hand with her and Walker in charge of getting the girls to safety. After Anri and Vorona enter the fray, they witness Anri's prowess with a Katana and immediately think of the Anime "Shakugan no Shana". After the fighting dies down, Erika starts asking Anri about Saika and even begins trying to search Anri's person for where she keeps Saika hidden.
Kyouhei manages to pull her off of Anri who decides to go look for Mikado.
Dragon Zombie ArcEditWhile she is hanging out with her cosplay team, Erika sees Anri near a bookstore and calls out to her. Erika introduces Anri to one of her friends named Azusa Tsutsugawa who occasionally hangs out with her and the van crew as well. She mentions how Anri should take up cosplay but Anri is less than enthusiastic.
Kadota's Coma ArcEdit
Erika is first shown in this arc talking to Anri about her relationship with Mikado and cosplay. Then Erika mentions Masaomi's return to Ikebukuro. While they were talking Erika gets a call from Kyouhei's father. Kyouhei's father informs her that Kyouhei was in a hit and run.
She, Anri, Walker, and Saburo arrive at the hospital and find that Kyouhei is alive but in critical condition. Walker and Saburo go to investigate who attacked Kyouhei while Erika stays behind at the hospital. Anri stays with her and tries to comfort Erika as they wait for Kyouhei to recover.
After hearing that Kadota's surgery went well she calmed down and told everyone that Kyouhei was okay. Near the end of the Arc, Erika smiles as she swears that she'll kill the person who did this to Kyouhei.
Saving Izaya/Haruna returns ArcEdit
While Erika and Anri are still waiting for Kyouhei to awake in the hospital, Izaya approaches the girls as Anri was preparing to speak to Erika about Saika. Anri confronts Izaya about Mikado and Masaomi’s situation only for Izaya to turn the conversation into a verbal assault on her. When Anri approaches tears, Erika grows serious, cutting the other two’s conversation off and stating she’ll solder Izaya’s eyelids shut if he makes her cry. Once Izaya leaves, Erika consoles Anri and forgives her for any wrongs she might have previously committed.
Final Curtain Arc Edit
After Kyouhei escapes from the hospital, Erika leaves on her own to search for him, but gets caught up in the horde of Saika children swarming around Tokyu Hands. Left cornered, Erika puts on the red contacts she had for cosplaying purposes and imitates the Saika children in order to blend in to the crowd and avoid being slashed. While making her way through the mob, Erika overhears Nasujima’s orders to seize Mikado and Kujiragi, and she leaves in an attempt to warn them. Afterwards, she heads in the direction of Shinra’s apartment and reunites with the rest of the van gang. Seeing her red eyes, Walker runs out to restrain her while Anri prepares to cut Erika with her own Saika and relinquish her friend from the other user’s control. Erika hastily explains the situation, and the two stand down. After Izumii and his lackeys attack the van on its way to Tokyu Hands, Erika stays behind with Walker, Kyouhei, and Saburo to hold off the delinquents while the rest of the passengers escape.
Durarara!! SH Edit
In Durarara!! SH volume 3, the perpetrator to a series of serial assaults is said to be seen attacking civilians while dressed as a character from a multimedia series that Erika and Walker are fans of. Angered that the criminal is ruining the reputation of the series, the duo commission Snake Hands to find the suspect and bring him in for a “little talk.” When meeting up with Kuon and Yahiro to discuss the details of the case, Erika is intrigued by their friendship and begins shipping the two.
- Main article: Walker and Erika
- Main article: Kyouhei Kadota
Erika has been with Kyouhei and his group for several years and are extremely loyal to him, following him in defecting from the Blue Squares without question or thought of consequence, and later following him in joining the Dollars. When Kyouhei was beaten into a coma in volume 10, Erika immediately drops everything to see him in the hospital. During her stay, she swears vengeance while smiling maliciously. In the side stories, it is implied that she has feelings for Kyouhei, but these are never elaborated on or addressed in the main series. Kyouhei is sometimes annoyed when Erika is overly fanatical in her interests in anime and manga as well as torture, but he still cares for her deeply.
- Main article: Saburo Togusa
Erika has been friends with Saburo for several years. The two were loyal to Kyouhei when they were members of the Blue Squares and followed him in leaving the gang and later joining the Dollars. The two share a desire to not lead a quiet life. Although Saburo does not share Erika's same enthusiasm for anime and manga, he still considers her to be one of his closest friends.
- Main article: Anri Sonohara
After the incident with Toramaru and after witnessing Anri use Saika to fight Vorona, Erika and Walker started asking Anri all kinds of questions about Saika, most of which she wouldn't give a straight answer to. Erika and Anri spent more time together after everything quieted down and became good friends afterwards. Erika tries to get Anri to take up cosplaying and even convinces her to try on a few outfits but has very little success. When she learned that Kadota was attacked she rushed to the hospital with Anri, who stayed with her the whole time. Erika then stood up to defend Anri against Izaya, by saying she was Anri's friend when Izaya mentally broke her with what he intended to do to Masaomi and Mikado.
- She is an avid fujoshi (female yaoi fan), as shown when she excitedly suspects Shizuo to be in love with Izaya despite their raw hatred for each other. This is shown again after the incident with Toramaru, when she expresses a desire to see Kyouhei and Chikage get together.
- Erika's name is a reference to the light novelists Mamizu Arisawa and Erika Nakamura.
- Narita has said that Erika's love for the 2D world is probably too strong for Saika to even work.
- The name of Erika's cosplay circle is Glasses Boys: The Double Shotgun.
- Erika's cosplay name is Eternal de Charmante.