Who is the guardian of the four heavenly gates in the journey to the west?

Nantianmen, the guardian of the Four Tianmen, is the Jade Emperor, the Taiyi Buddha at the East Gate and the Tathagata at the West Gate. Beitianmen is the Zhenwu Emperor.

The guardians of the worse gate are Tota, Li Tianwang, Nezha, the Four Heavenly Kings and the Hundred Thousand Heavenly Generals, and they are directly led by the Jade Emperor.

The guardians of the East Gate are Taiyi Salvation Buddha and Nine-year-old Sheng Yuan, but Taiyi Salvation Buddha wandered around the Three Realms all day, helping others everywhere, so the task of guarding the East Gate was handed over to Nine-year-old Sheng Yuan.

The guardian of Beitianmen is the Zhenwu Emperor in the north. It is said that the ancient Zhenwu emperor descended from the sky and led a small number of troops to level the north. After that, Zhenwu Emperor had a resounding name, that is, "the originator of swinging demons".

The Monkey King had seen three other immortals in heaven, but Simon Tathagata had never seen them. Without knowing its strength, he ventured back to Huaguoshan from Simon. It was this Tathagata who let the Monkey King go, so this is why the Jade Emperor of Heaven invited Tathagata instead of him.