Blue Squares

The Blue Squares is a color gang that fought with the Yellow Scarves many times. Their conflict with the Yellow Scarves was orchestrated by Izaya Orihara and ultimately led to the downfall of both the Yellow Scarves and the Blue Squares.

After the Blue Squares' kidnapping of Saki, some members of the Blue Squares were arrested by the police while some others joined the Yellow Scarves. Masaomi Kida goes and talks to a member of the Dollars and former member of the Blue Squares, Kyohei Kadota, about the Blue Squares.

According to Kyohei's friends, they say the Blue Squares never existed meaning Masaomi was fighting with a gang that never existed with the implication that the Blue Squares was a tool of Izaya Orihara to manipulate the color gangs of Ikebukuro, and through it the head of the Yellow Scarves, Masaomi Kida.

Trivia

 * As the name Yellow Scarves is a reference to the Yellow Scarves Rebellion, it is possible that the name "Blue Squares" could be a reference to the "Blue Sky" referenced in the he Rebellion's slogan. The slogan is “The Blue Sky has perished, the Yellow Sky will soon rise; in this year of Jia Zi, let there be prosperity in the world!” (蒼天已死，黃天當立. 歲在甲子，天下大吉. ). In the context of the original rebellion, the Blue Sky was a reference to the Han Dynasty, the Yellow Sky was the rebellion, however, it is entirely possible that Izaya would have seen creating the Blue Squares as a poetical opponent for the Yellow Scarves.
 * Aoba has been quoted saying that the name "Blue Squares" was originally thought up by a sickly charcter known as Yatsufusa (from Etsusa Bridge?) and the origin being that they "were almost like 'sharks stranded in shallow shoals.' Each one of us had a small blue rectangular piece of territory. You guys are like sharks fighting desperately just to protect that little slice of territory you have"
 * As of the end of Volume 6 of the Light Novels, Mikado Ryugamine is now the "leader", of Blue Square. However, Aoba plans to overthrow him at some point, and re-take control of his gang, and Mikado's gang, Dollars. It is hinted that he may do the same plan he did with Ran Izumii, with Mikado, just as Izaya was going to do (mimicking the Kida and Saki incident).