So...to answer my own questions:
In 1876, the Taiho Code, set the age for taxation and military service at 21. (this would mean they were 20 by today's standards as back then when you were born you were considered 1 and so on..also note, nothing about adulthood, booze, voting or marriage though...just taxes and military responsibility) Through the Edo period, there was a ceremony called “genpuku” performed in various sections of society marking the attainment of manhood. The age a boy went through the ceremony differed depending on rank, but was usually performed at the age of 15 (14 by today's standards) for the samurai class. When the 1898 Civil Code was enacted, the most common age of majority in the West was 21. The Meiji government set the age with an eye to the West. The sudden jump to 20 years of age was made to bring Japan close to the Western standard but kept under 21 as some at that time claimed that Japanese people developed more quickly than Westerners.
Soooooooo....while the age of adulthood was lower than in foreign countries at the time, most countries have lowered their own legal age of majority and Japan is still stuck at 20.
Tokyo Gov. Shintaro Ishihara,for example, does not want 18-year-olds to be allowed to vote.
At a news conference in February, Ishihara pointed out that parents often have to accompany their 20-year-old offspring to the annual coming-of-age day ceremonies sponsored by local governments to prevent the "new adults" from disrupting the events.
Even 20-year-olds "are essentially not adults," Ishihara said.
Hate young people much?
While not alone, there aren't many other places that the age of majority is 20 or above:Age 20
Japan, New Zealand
, Taiwan, ThailandAge 21
Bahrain, Chad, Egypt, Honduras, Kuwait, Lesotho, Madagascar, Namibia, Singapore, Swaziland, United Arab Emirates, Mississippi
, Puerto Rico, Zambia, Azerbaijan