Yonkō

The Yonkō (もちろん, Four Emperors) was a term used to address the four most powerful rouge shinobi alive. Each were almost equal to each other in power, and the group had no real leader. Though they did fight together on some occasions, mostly, the four Yonkō were large rivals with each other.

Overview
It is unknown when the Yonkō formed officially, however, at some point after their individual defections form their respective home villages, the four members made a name for themselves as "Yonkō". The first known contact between members of this group was a battle between Ryun Uchiha and Seireitou Hyūga, which is said to have birthed the two's rivalry.

Though the group was known to fight against significant threats, they rarely fought as one unit. In fact, most of the time, the group fought among themselves, trying to determine who was the strongest Yonkō, though none has ever been decided upon. Because of the looseness of the group, there is no official leader, though each member of the Yonkō have taken turns in a "leading" role when the group needs it most.

Trivia

 * Ryun and Seireitou's rivalry closely resembles that of and 's own rivalry.