BASIC MEANING
Dual citizenship occurs when one person acquires nationality from more than one country. This can happen when a child is born of parents of mixed nationality or of parents who are living in country other than that of their citizenship.
CURRENT SITUATION
Nowadays, a child born in Japan of mixed parents would be eligible for both Japanese citizenship and the citizenship of their foreign parents. However, Japan takes a stricter view of individuals holding more than one nationality, since the situations and laws can easily become a bit complex. Therefore, when young people become adult, about 22, they have to choose their citizenship.
Unlike many countries that tolerate but not officially endorse dual citizenship, Japan chooses to take restrictions on dual nationality. Thus, when a Japanese national holding a foreign nationality turns 20, they will be required to choose on sole citizenship within 2 years.
THE GOVERNMENTAL MEASRURES ABOUT HOW TO CHOOSE YOUR NATIONALITY
For Japanese citizens holding a foreign nationality, there are two methods of declaring a single nationality. One is abandoning the foreign nationality, the other one is swearing to Japanese nationality. When the time comes to choose one nationality, people are usually supposed to think carefully and make the right decision.
MY OWN OPINION
In my own opinion, the actively cracking down on dual nationality in Japan may be a wise choice, even though the practice to require one to make a decision seems a little cruel. But what I am thinking of is that it’s better for one to choose which country one belongs to. In this way, it will be more clearly who is responsible for you, but you don’t have to cut the tie with the other country. It’s just like choosing your belief. To our motherland, we should become a faithful, loyal and devoted national.
By Yan Yinyan
JAPANsociology 
I have never asked to choose between two nationalities, but it sounds cruel forcing us to choose one in between. For instance, I gave up the nationality of being a Japanese, every time I visit Japan, I will have to line up in the foreigner line at the immigrant. This make me feel distanced from this country. Though we could still keep the tie with this country, its just not as easy as entering the country by lining up in the Japanese line. I think this is minor but important, this shows how close I am with this country.
I agree with your opinion. I believe people should choose what country they would like to call their own. I was born in Scotland and then raised in America. I had duel citizenship until I was 18. I had to choose American or Scottish. I chose American of course due to my family being American originally and also because college would be even MORE expensive if I were Scottish. I haven`t been to Scotland since I was 2…so truly I don`t know the feeling of being there and being American, not Scottish. Someday I would like to go visit, but I believe that i will still consider myself American with a Scotch-Irish lineage.
Japan asks that one choose Japanese or a foreign nationality but even if you choose Japanese the other nationality does not go away. So technically while you are in Japan your foreign nationality is null and void and while you are in the US your another country your Japanese nationality is null and void. In many cases, increasingly in the US as well, renouncing nationality is not longer a simple process. American has been known to deny renunciation requests for various reasons. There is often a 1-2 year waiting list to speak with the vice council.
The Japanese government clearly states that you must choose one nationality by either choosing one at the ward office, or renouncing your other citizenship. I have never heard of anyone being given two years to renounce after they have obtained Japanese citizenship, although there are stories circling that this may be the case for some.
One more thing; be wary o articles posted on the “Becoming Legally Japanese” website. http://www.turning-japanese.info/
I have seen too many dubious articles there, and there is no way to leave comments or contact those involved. This makes me very suspicious of the materials on this site.