Where does the tea ceremony in Japan come from?

The tea ritual in Japan has its origins in China and Buddhist monks.
Before we talk about the origin of the tea ceremony , let’s talk about the origin of tea. Unsurprisingly, tea comes from China, where it has been used for millennia first as a medicine and later as a consumer product.
But how do we go from  purely medicinal consumption to daily consumption? Buddhist monks are not allowed to drink alcohol and to stay awake during their meditation, they started drinking tea. Little by little, the use spread to the aristocracy before becoming popular in the lower classes.
Today, tea is still part of the daily life of the Chinese . In China, the water is not drinkable, so tap water must be boiled before it can be drunk. Therefore, it is common to infuse some tea leaves or other herbs to give boiling water a pleasant flavor.
Tea appeared in Japan in the 9th century, imported and popularized by the Buddhist monk Eishu. It was first consumed by the Japanese nobility before spreading to the rest of the population in the 12th century. Changes take time!
Regarding the tea ceremony, it was  influenced by Zen Buddhism , since it derives from the book by Lu Yu that mentions the temperature and the utensils that should be used to drink tea in the 8th century.
However, it evolved a lot until the 16th century, taking elements established by the samurai and the popular classes. But the philosophy of the tea ceremony was codified mainly by the priest Murata Shukou and Sen no Rikyū, who developed the key concepts ( sei, kei, wa, jaku ).
Currently, the tea ceremony is rarely practiced in Japan , but it is a strong symbol of the country’s culture and history. Even the Japanese do not always know the development of the ceremony and attend only once or twice in their life. Where does the tea ceremony in Japan come from?