adopted child gaining citizenship

I've been doing some research about how teens can become a japanese citizen, but I've never actually read anything about adopted children. Suppose a girl is adopted by her uncle, who is a japanese citize. Can that girl become a citizen, too?

Even adopted by a Japanese citizen, the person with foreign citizenship cannot obtain japanese citizenship by adoption.

If the person want Japanese citizen, the only way is to get naturalized.

Related article (sorry I coudl find it only in Japanese language.)
http://www5a.biglobe.ne.jp/~ksoffice/page41.html

It's possible for you to be naturalized as a Japanese citizen if you are adopted by a Japanese. Read the following:

http://www.moj.go.jp/ENGLISH/information/tnl-01.html