Article 731 to 737 of the Japanese Civil Code stipulates the following requirements: The male partner must be 18 years of age or older and the female partner must be 16 years of age or older. A person who is under 20 years of age cannot get married in Japan without a parents approval.
Is it rude to wear shorts in Japan?
As I mentioned in the intro, you should be fine wearing shorts as you walk around Tokyo. This goes for both men and women. Speaking of womens dress code, theres pretty much no limit on shorts length. For the most part, though, Japanese people tend to dress warmer than what the weather calls for.