Question

Which event occurred first?

Answer 1

Mongols took over Chinese rule in 1279
Tokugawa Shogunate began in 1600
The Koryu dynasty (aka Goryeo) began in 918.
Buddhism was already introduces into Japan in 552 AD.

So first it was Buddhisim in Japan, then Koryu dynasty, then Mongols in China and then Tokugawa Shogunate.

Answer 2

Answer;
Buddhism was introduced into Japan

Explanation;
Mahayana Buddhism was introduced to Japan from Korea in the sixth century, in either 538 or 552. This happened when a delegation sent by a Korean Prince arrived at the court of the Emperor of Japan, who brought with them Buddhist sutras, an image of the Buddha, and a letter from the prince praising dharma.

The other events came way after the introduction of Buddhism in Japan
Mongols took over Chinese rule in 1279
Tokugawa Shogunate began in 1600
The Koryu dynasty (aka Goryeo) began in 918