Birthdate: March 21
Height: 165 cm
Weight: 50 kg
Blood type: O
Hobby: Net Surfing
Likes: Living a different life, Sonohara Anri
Dislikes: Living a normal life
Handle: Tanaka Tarou (田中太郎)

The primary male protagonist of the series, Mikado Ryugamine is a high school boy who moved to Ikebukuro with the encouragement of his best friend Masaomi in order to search for unusual beings and adventure. Mikado tries hard to change his image but so far he has not had any luck. Mikado has had moments where he speaks his mind, which is a reason why Masaomi admires him.

He is the creator and the leader of the anonymous online gang: Dollars. He doesn't have much authority inside Dollars, since he believes Dollars is a group "without rules." However, Mikado changes his mind after Dollars is corrupted by its bad members. He becomes the leader of the Blue Squares gang, which has largely infiltrated Dollars, after being offered the position by Aoba.
In the light novel volume 6, he is shown to have a darker side or true self, being able to stab Aoba's hand with a ballpoint. Aoba notes that maybe Mikado has yet to show his true self.
Mikado's true colors are further revealed in volume 8 of the light novels. Mikado and the Blue Squares confront and corner Adabashi Kisuke who has been terrorizing Ikebukuro for several weeks with his henchmen. Adabashi attacks Mikado, severely injuring him. However, Masaomi arrives in time to save Mikado from getting killed. Before they could exchange greetings, Mikado pours gasoline on Adabashi as he tries to get up, he then calmly lights Adabashi on fire. Masaomi is shocked at the level of cruelty that Mikado had shown and is disturbed at how Mikado can simply smile through it all. He yells at Mikado for what he was doing but Mikado simply brushes him off by telling him to "mind his own business" and walks away.