According to Wikipedia the first known references to tea occured in the 9th century, when Buddhist monks introduced tea, a drink made from Camellia sinensis to Japan.
The Camellia variety sinensis is not native to Japan, (or not considered so, anyways,) but there are actually other Camellia species that are native to Japan, such as japonica and sasanqua, and they can be used to make a similar tea beverage. Japonica is pretty much in the name, sasanqua is native to China and Japan.
I wonder why there seems to be no apparent evidence that these other plants were used before Camellia sinensis.
Also, something about the ancient writing systems of Jindai Moji—in reference to what is little known about ancient Japan, even though many believe the entireity of these these writing systems are more recent forgeries.