In Chinese literature, the Four Seas are a metaphor for the boundaries of China.
In Chinese mythology, East Sea is the domain of Ao Guang, the Donghai Longwang (東海龍王), or "the Dragon King of the Eastern Sea", who is responsible for controlling its storms and tides.
In the Classic of Mountains and Seas（《山海经》）, the Dragon King of the East China Sea is the god of the rain department, but it maintains a greater special freedom, and human rainfall is completed by the dragon King of other rivers, lakes and Wells, and rarely needs the East Sea Dragon King to rain himself.
The power of maritime jurisdiction is owned by the dragon King, and the Heavenly Court is generally autonomous.
In China, the eastern Wei is respected, and according to the Zhouyi《周易》, the East is Yang, so it is natural that the Dragon King of the East China Sea ranks first.