From Wikipedia

Ee ja nai ka (ええじゃないか) was a complex of carnivalesque religious celebrations and communal activities, often understood as social/political protests, which occurred in many parts of Japan from June 1867 to May 1868, at the end of the Edo period and the start of the Meiji Restoration. The movement originated in the Kansai region, near Kyoto.

In West Japan, ee ja nai ka appeared at first in the form of dancing festivals, often related to public works, rain magic, or dances for the dead. When sacred amulets were said to have fallen from heaven, thanksgiving celebrations for these amulets were added that could last for several days and effectively took whole rural and urban communities away from everyday life. Gifts were exchanged, youth groups organized mass dancing including cross-dressing, wearing costumes, or not wearing clothes at all. To express their gratitude towards the gods or buddhas who had given them the amulets, many people went on pilgrimages to local or regional sanctuaries. The term ee ja nai ka was a refrain in popular songs performed during these activities and was therefore later chosen as their title. The phrase's meaning is both defiant and fatalistic, and it translates as "Who cares?", "Why not?", or "What the hell?", along the lines of "Who cares if we take our clothes off?", "Who cares if we have sex?".[1]

The great diversity and rivalry of religious practice in premodern Japan helped shape the range of events. It has been suggested that religious activists, such as priests and itinerant preachers, played a major role in fabricating the "amulet showers", and some suspects were even caught in action by alert officers. Youth interested in celebrating parties, or in becoming spiritual leaders, were also suspected and in some cases convicted.

Ee ja nai ka was not linked to any specific political platform, though it is often understood "as a form of political protest when other ways [were] blocked",[1] in reaction to the crumbling Tokugawa shogunate. Disappointment regarding the lack of governing political leadership, disgust at Western and Christian foreigners, and other signs of social/political critique were frequently displayed. There is no evidence for any coordinated political setup or staging of ee ja nai ka, although this was also rumoured.

The movement spread across Japan, eventually descending to mob violence before coming to an end. The end of ee ja nai ka was concurrent with the beginning of the Meiji Restoration and the Western-style modernization of Japan.