Oh, if not for your blog about Tanabata, I would have never known there is a 'Double-Seventh festival' in Japan, too. It is really interesting to learn about the history links among different countries and regions. Last time I just learned the origin and spread of Oden from your blog. I doubt if there is 'Dragon Boat Festival' in Japan. If so, is there also a beautiful but sad love story--Madam White Snake associated with 'Dragon Boat Festival' ？ It seems that in Chinese folktales the true lovers are always forced to seperate...
It is said that on the 'Dragon Boat Festival' which is a very old festival in memory of QuYuan, the herbal medicines have the strongest effect on exorcising the evil spirits. Except eating the Zongzi, in some other places of South China, people may hang the mugwort on the wall or door and drink the realgar wine which can make demons reveal their true features in the folktale.
Here is the story of 'Madam White Snake'.

P.S. I just check the origin of this story online. It shows it was born in Ming dynasty, matured in Qing dynasty. Oh, a big surprise to me! Just a near-term legend, although the story being set in the Southern Song Dynasty(should be after the Heian period of Japan). It must not be so popular as the story of Cowherd and Weaver outside China.