A young glasses-wearing girl that attends the same school as Ryugami Mikado and Masaomi Kida. She is very quiet and reserved.
Anri spends time with Mikado and Masaomi
Anri Sonohara was born in Ikebukuro to a pair of loving parents whose father was an antiques dealer. Five years before the start of the series, her parents died in what was considered a burglary where she was allowed to live for some reason. She always led a quiet life and attracted to others quickly, not saying much and considering herself a parasite. Anri was friends with Mika Harima in middle school but just before their high school year began, Mika mysteriously disappeared. Anri continued to be quiet until she slowly became friends with Mikado Ryugamine and Masaomi Kida.
Anri is also in possession of a demonic weapon called Saika which takes over people with their love. Since Anri closed off her heart and is incapable of feeling love, the demonic force can't control her body and she uses it with elegance and grace.
In the beginning of the series, Anri is an extremely quiet and shy girl who stays by herself most of the time. She used to rely on Mika for interactions and friendship but finds herself all alone with no one to really call her friend. As the first year of school continues, she takes the courage to volunteer herself as a class representative with Mikado joining in to for similar reasons in that she wanted to do something that she normally wouldn't do. As she spends more time with Mikado, she finds herself also hanging out with Masaomi who claims to find her ero-cute, a portmanteau of erotic and cute. However, she only sees the two as just friends.
After the Slasher attacks though, she is able to become more independent and happy about life even though she still relies on others. She is shown to be a good and caring friend to the two boys and spends all the time she can with them since they are close friends of her. She does not reveal her relation to the Slasher attacks or her past with them but continues to look to the future with a smile on her face.
Major Story Arcs
Looking for Mika
Anri spends the first few days of school trying to find information about her friend Mika who went missing a day before school started. She tries to fit in though by becoming class representative, saying it'd be something Mika would do.She asks Seiji Yagiri if he knows anything since he was the one Mika was stalking. Anri finds a girl that looks almost identical to Mika but its not her. As a result of her looking around, she is cornered by three ganguro girls from her school who bully her since Mika is not around. They try to get their friend, a so-called member of the Dollars, to jump her but Izaya Orihara, Mikado, and Masaomi intervene to help. Even when the Dollars come back and Shizuo Heiwajima fends them off, Mikado takes Anri and runs off with her. Anri promptly thanks him and leaves. Anri tells Mikado and Masaomi that Mika was a stalker and her obsession may have lead to her disappearance.
Anri tries to live life normally but finds herself getting harassed by Mr. Nasujima, a perverted teacher, who claims she should thank him for getting her and Mika in the same class. Masaomi comes by and reminds the teacher about Haruna Niekawa, a girl from last year who left because of a relationship they had. The teacher backs off as Masaomi vows to guard her from his attacks. She also finds her shoes missing that day as well. Mikado spends extra time after school finding them as Anri simply says thank you and closes her door behind him.
Soon after, the truth about Mika comes to light at the massive meeting of the Dollars in Ikebukuro. Since Anri was not a member of the Dollars at that time, she has no idea about what happened or why Mika got plastic surgery. All she knows is that her friend is back in school.
The Slasher Attacks
Six months after the Dollars meetings occur, Anri is now a good friend with both Mikado and Masaomi but still tends to be reserved about things. What scares her the most are the recent Slasher attacks in which victims are attacked but not killed. Anri tries to calm down but is still uneasy. One day after school though, she is approached by the three ganguro bullies from before as they proceed to berate her and mock her for being a leech. Anri notices a black figure with red eyes approach from behind as the Slasher attacks the three victims. Anri is spared though for some reason as Mikado and Masaomi rushed to the police station to retrieve her.
The next night, she is attacked again by the Slasher who is shown to be the magazine reporter Niekawa. Just as he is about to attack, Kadota, Saburo, Walker, and Erika hit him with a van. Despite that, he is still moving about. Shizuo and Celty arrive on the scene since the two promised Mikado they would take care of the Slasher. Shizuo rips the door off of Saburo's van and assaults Niekawa. Anri thanks them for saving her as Celty takes Anri home but is approached by Haruna Niekawa, Niekawa's daughter. Haruna claims she fell in love with Nasujima and scorns Anri for being the one Nasujima loves despite her not liking him. It is revealed that Haruna is the Slasher and can control her victims since her attacks spread and feed off of love. She calls in her army to take care of Anri as she chases down Nasujima.
Anri appears and withdraws Saika, the real demon blade that Haruna thought she had. When Haruna is poked by the blade, she sees Anri's past. It turns out that her father was a failing businessman and as a result, he took out his frustration on his wife and Anri. Anri, as a result, closed her hear from love in any capacity since this was the life she lived. As her father is choking her one day, her mother uses Saika to kill him then herself. Anri then took the blade and was able to resist its call since Saika feeds off love and there is no love in Anri's heart. Even though she is harmed by Haruna, Anri is able to subdue Haruna and all her minions are taken out of the trance. Celty arrives and thanks Anri for her work, letting her know that she wouldn't fight her as the Slasher since she knows she would lose. She tells Anri to use the power of Saika to try and do good for Ikebukuro as Anri goes to the hospital for treatment.
When Anri is released from the hospital, the Yellow Scarves finally are brought back together under their old leader Masaomi. His intentions are to avenge Anri for the attacks of the Slasher and will go after the Dollars too if they were involved. Mikado does something similar as he puts out the word about the Slashers. As time goes on, Masaomi leaves suddenly as Anri begins to worry about them. She joins the Dollars instant chat board, adopting the name Saika and becoming fast friends with Setton. She tries to not worry but Izaya continues to provoke her. One night, she follows Masaomi to the docks and discovers his secret. She tries to escape as she calls Celty to help her out of the jam.
Anri displays her power to the Yellow Scarves
When Celty arrives to save Anri, Anri uses her powers as the Slasher to evade attacks made by Horada. This confirms a suspicion that the Dollars and the Slashers are one in the same. Things grow tense between the three friends as the attacks on random Dollars members by the Scarves continues. Anri uses her power as the Slasher to subdue members who were attacked by the original Slasher and control them to stop the attacks. However, as a result, other members of the Scarves saw her and describe her to Masaomi as a girl in a Raira uniform, with glasses and big breasts. Masaomi realizes who it is. When Anri is cornered by the Scarves, Mikado rounds up the Dollars to save her. Masaomi confronts her and accuses her of being a whore and lying as she smacks him and runs off.
Anri gets caught by Horada and his gang as Shizuo confronts them and fends them off, recognizing Anri but forgetting who specifically she is. Celty arrives too and brings Anri back to Shinra Kishitani's apartment. He lets her stay there for the time being to hide from the Scarves and figure things out. Celty asks Anri if she knows how Mikado is involved since he is the leader of the Dollars. She admits she knows nothing as Celty goes to get Mikado. In the meanwhile, Shizuo arrives as he was shot and needs Shinra to help. He reveals that Masaomi supposedly ordered the hit but knows it wasn't him thar ordered the hit. Anri leads to the factory to help stop the war.
Arriving at the Scarves hideout, she uses her power to subdue some of the Scarves which saves Masaomi's life. She slashes through the door and soon Mikado and Celty arrive. The Dollars emerge from the Scarves and take them down as Mikado and Anri help Masaomi to Saburo's truck to take him to the hospital. After he's dropped off, Anri uses a possessed Scarf to encounter Izaya as she attempts to kill him but he evades her and gleefully leaves. When Masaomi leaves with Saki Mikajima, Anri worries about him but Mikado comforts her to let her know that Masaomi will be back soon.