The obvious sites that people have heard of are forums such as 2ch and 2chan. These are online message boards where people can anonymously post (anonymous being the operative word). 2ch is a Japanese-text only board, whereas 2chan is a board just for images. Another site that periodically posts anime top 100 charts is NHK news. NHK is one of the major news distribution companies in Japan.

The closest equivalent to a Japanese version of MyAnimeList (MAL) would be anikore.jp. The site is split into several major sections: all anime, individual categories, anime by broadcast date, and individually made lists. Individual categories are further split into: currently airing, based on a manga, best OP (anime opening), and various other distinctions. It's very thorough and easy to sift through (if you read Japanese). The major functions of the site are for posting a review, voting for anime, and creating a ranking list that others can view and vote on as well. There are no forums that allow for back and forth discussion or reviews of individual episodes of an anime season. So, you can see how the site varies greatly from MAL.

Some Japanese fans have explained that most fans do not like to "individualize" their online persona. Registering an account on an online forum-type site still leaves traces of personal information. As a society, Japan is very concerned about identity theft and having any type of personal information floating around in cyberspace. For example, if a teacher posts a picture of themselves at a school festival or sporting events on their social media profile, they will go as far as to blur out images of their students' faces. They view the internet as basically one large social media platform. Privacy is very important, especially in the case of minors.

If a controversial comment is posted on an online forum, it is possible that the account could be traced back and the real identity could be determined. It may sound strange, but it could honestly hurt someone's real-life reputation if it was determined this person was an "online troll". Japanese culture values harmony and not voicing strong individual options. They try to stay as inconspicuous as possible while online. If they're going to post their opinions and subjective reviews, it's going to be through a site that allows them to stay as anonymous as possible and doesn't allow for much back and forth discussion. Maybe, now you can see why polls (such as the ones from NHK or various manga publication companies) and anonymous message boards would be where many Japanese fans voice their opinions.

One other thing we wanted to mention, is that Japanese fans are much more willing to spend their hard-earned money purchasing anime DVDs, Blu-rays, original soundtracks, figures, etc. Anime studios can tell how popular their shows are through merchandise sales and pre-order numbers. It's a much more consistent and prevalent statistic in Japan compared to western countries.