I am not a lawyer so I'll make this quick.
NihongoPeraPera collects general information about all visitors to the site, including what country you come from, what web browser you are using, and what links you click on. I use this information to improve the site, and it is not sold to advertisers.
If you do leave your e-mail address when you comment on the site, I may occasionally send you an e-mail instead of answering your comment on the site itself. I do this to cut down on the amount of posts on each page, so that people who are looking for information don't have to read a whole forum thread just to get the gist of what people are saying.
I use Google Analytics, Adwords, and Adsense on this site. For more information about what Google does with your information, and how to opt out, visit Google.