Mikado Ryugamine is a student who moves to Ikebukuro to start his new academic career. He is known for being reserved and shy about many things.
Mikado meets with his childhood friend Masaomi
Mikado Ryugamine was born in the country areas of Japan and grew up as an average kid with nothing to do really. He was friends with Masaomi Kida but he moved to Ikebukuro sometime before the series started. When he was in middle school, he got his first computer and used it to chat with Masaomi about different things. However, his boredom with a normal life got the better of him as he decided with two other people he knew to start a fictitious gang called the Dollars that no one would be able to identify. It went great until someone leaked the password and membership imploded, leaving violent acts all around the area of Ikebukuro. The other two founders left as Mikado was able to convince legitimate members of the Dollars to do good things to counteract the bad ones.
At the insistence of Masaomi and a desire for a new change, Mikado applied to Raira High School and moved to Ikebukuro to attend with his friend.
When Mikado first moves to Ikebukuro, he is shown to be a reserved and shy teenager who keeps things to himself rather than tell others how he is feeling. He develops a crush early in the school year on Anri Sonohara, a girl who nominated herself to be class representative. Although he usually plays comic foil to Masaomi, he tends to keep things as calm and relaxed as possible especially when Masaomi goes out of his way to try and do something crazy or stupid.
However, once he reveals himself to be the leader of the Dollars, his mood changes from shy to confident as he rallies other members of the Dollars to help him with a crisis. When the attacks by the Yellow Scarves starts to occur, he gets nervous as his confidence slowly wanes away while he worries about how to handle the situation without becoming a burden or involving his friends in the violent struggle. By the end of the series after the gang war, he is shown to be more alive and positive about things as he knows he has to make each day special or else he will end up in the boring cycle of life in Ikebukuro.
Major Story Arcs
Life in Ikebukuro
Mikado moves to Ikebukuro to attend Raira High School with his old friend Masaomi Kida who he has been in contact with via the internet. While Masaomi gives Mikado a tour, he warns him of the old color gangs like the Yellow Scarves and the Blue Squares that used to exist in the area and introduced him to a few friends. The first group he meets are Kyohei Kadota and his friends Walker, Saburo, and Erika; all of which are good friends of Masaomi. They welcome Mikado to Ikebukuro as Masaomi introduces Mikado to Simon, the Russian man who owns his own sushi store. As the day comes to an end though, he is warned to stay away from the information broker Izaya Orihara and never to piss off Shizuo Heiwajima. He also catches a glimpse of the mythical Headless Rider on his first day in the city.
Mikado witnesses two of the toughest men in the city fight.
As the school year starts, Mikado becomes smitten with his classmate Anri Sonohara and volunteers to join her as class representatives. Mikado wants to know more about the Dollars as most people tell him various things, Kadota warning him to stay away from the group. He sees Anri getting bullied by a group of ganguros and so-called member of the Dollars as Izaya helps him to save her and scares away the bullies. Mikado also witnesses the strength of Shizuo who assaults Izaya with a vending machine. Mikado is able to get Anri out of there when a group of Dollars picks a fight with Shizuo as he feels better about moving to Ikebukuro.
As times goes on, Mikado becomes good friends with Anri, who spends time with him and Masaomi before and after school. He also tries to discover how Mika Harima went missing to help Anri, thinking that Mika ran of with Seiji Yagiri. Mikado questions Seiji about it but claims to know nothing as he and a mysterious girl who closely resembles Mika leaves with him.
Looking for the Head
Life continues normally for Mikado with school and life until the girl with the scar around her neck bumps into him. She begs him to save her as Celty rounds the corner on her bike. Mikado agrees and runs off with the girl who he brings back to her house for safety. She claims to have amnesia and doesn't remember much as Mikado allows her to stay there. He tells Masaomi who thinks that Mikado has fallen for someone but he tries to play it down. After discovering one of their classmates is a member of the Dollars, Mikado is approached by Celty and Izaya.
Celty asks Mikado for his help.
Celty explains what is going on to Mikado that the girl with the scar is also called Celty and that that is her head. She asks Mikado to help as he agrees on the condition that Celty show him what's behind her helmet. She agrees to show him she has no head as he revels in the fact that something as cool as Celty can exist. He brings them back to his apartment and lets them know she might run so he volunteers to talk to her. Mikado finds her gone as he is attacked by two members from Yagiri Pharmaceuticals demanding to know where the girl went. Celty recognizes their truck and breaks in with Izaya, saving Mikado as they flee. Mikado realizes they'll need help as he logs on to the Dollars' website to organize something.
In the city, Mikado offers to meet with Namie Yagiri, the head of the company and Seiji's sister who wants Celty's head back. She goes to meet with him as he theorizes that Mika is dead and that she transplanted Celty's head on to her body for her brother. Namie laughs it off as she orders her men to grab Mikado. Mikado sends out a mass email to all the Dollars as it is revealed he is the leader of the Dollars and that everyone except for Namie and her men are members in the square. Mikado is able to flee as he is attacked by Seiji. Celty saves him as she wants her head back. It is explained though that what she thought was her head was actually still Mika, only she underwent plastic surgery to look like Celty at Namie's insistence. As the mob leaves, Izaya thanks Mikado for the fun and warns him life will return to being boring soon, calling him Taro Tanaka as he leaves.
Six months after the massive flash mob of the Dollars occur, things have gotten normal again for Mikado and his friends as they go to school and try to kill time. Also during the six months, the Yellow Scarves begin to regain power in Ikebukuro. At the same time, a massive series of attacks are carried about by someone called the Slasher who slashes their victims and leaves them alive. Mikado becomes increasingly distraught since people on the internet speculate that the Slasher attacks started at the same time the Dollars had their meeting, leading some to believe they are one in the same. He tries to figure out what to do as Celty approaches him, asking whats wrong as she tries to help him out. She tells him that she'll look into it as well since she has a score to settle from a few months ago.
Celty and Shizuo take care of the matter as the Slasher is revealed to be Haruna Niekawa a girl from Raira High School wielding the demonic blade called Saika. However, the actual owner of the blade is Anri as she came into possession of Saika after her parents died and defeats Haruna. After things settle down, Celty assures Mikado it was taken care of as he posts to all the members of the Dollars to report anything they know about the Slasher.
After the Slasher attacks, the Yellow Scarves regain their leader Masaomi Kida who vows to avenge Anri for the attack on her. As Mikado and Masaomi escort Anri from the hospital, the two worry about Masaomi leaving constantly. Mikado tries to figure out what to do as Izaya fills him in on some of the events between the Yellow Scarves and Blue Squares a few years ago without revealing who the leader is. As time goes on, reports of members of the Dollars getting jumped by the Yellow Scarves come in by the masses as a man named Horada is orchestrating the attacks against Masaomi's wishes.
As more members of the Dollars quit, Mikado tries to come to a solution as their leader on what to do as he never expected anything like this to ever happen. Mikado looks to his fellow members for advice and agrees that their tactics should be to protect the city from the Scarves. Izaya posts how a group of Scarves led by Horada are taking Anri away as Mikado arranges for another mass meeting to save her from the Scarves. Many members of the Dollars catch on and help Anri escape while intimidating and beating up some of the Scarves. Mikado is relieved that Anri is safe but is still confused about what to do. He ultimately decides to disband the Dollars, thinking that with no gang around, the Scarves will stop their attacks.
This proves not to be the case as Horada continues his assaults, going so far as to gun down Shizuo who is the fiercest member of the Dollars. Celty meets with Mikado as he explains his actions to her and tries to reason that things are better. She agrees but she tells him that Masaomi is in danger as he was ejected from the Scarves and is going to confront them. He goes with Celty to save Masaomi as he discovers Anri is the leader of the Slashers and Masaomi the leader of the Scarves. As they defend themselves, Kadota launches a surprise attack as members of the Dollars had infiltrated the Scarves since no one knows who is a member of the Dollars. Mikado, Anri, Saburo, Walker, and Erika take a badly injured Masaomi to the hospital while Kadota and Celty take care of the gang and Horada.
After Masaomi recovers, he leaves Ikebukuro with his girlfriend Saki Mikajima to simply get away from it all. Mikado grows close with Anri as he assures her that Masaomi will return. With everything calmed down, Mikado restarts the Dollars as they now silently own Ikebukuro.
It later turns out that Mikado actually created the Dollars, first as a sort of fun game, but then they grew large enough that he found he could use them to change things in the real world. In fact, he even used a mass text message among Dollars members to scare Namie and her thugs away after they threatened him.