Unique popularity of Twitter in Japan Market

Twitter is an important social media in Japan. In fact, the country is the 2nd largest user network region outside U.S., following Brazil. In Japan, the network is well competing with Facebook, and eMarketer reports Twitter's 27 million users outstrip that of Facebook which is 23 million aside from the largest network of LINE having 50 million users. (in 2017, before removal of fake accounts in Twitter)

Why is it so big in Japan? One of the reasons must be cultural fit of Twitter. 
First, Japanese language has advantage in tweeting, where it had limitation of 140 characters in one post. In English, the word "SUMMER" consumes 6 letters, but in Japanese, it's "夏", just a single character, so users can put lot more information in one post.
Also, anonymity of user account encourage users to utter a opinion freely in Japan, where arguing politics or criticizing something openly among friends is not very common.

Japanese users love to play in Twitter. With presumably help of it's homogeneous culture, a big event among Japanese users is tweeting a magic spell of "balse" all together at the same time when their favorite anime movie "Castle in the Sky" is shown on TV roadshow at the moment hero and heroine utter the word. This posts topped the Twitter's record of 11,349 tweets per second in Nov 2017, exceeding the 2nd record high posts when the news of Beyoncé's pregnancy came out. Users are so excited to report about Twitter's server capacity tolerates this heavy flash stress every time after this anime is on TV. (Twitter CEO Seemed Unaware Of Japan's Most Famous Twitter Meme) In addition, not very often but some times people play with posts by creating vertical sentence, which could be familiar for Japanese as vertical writing was the traditional style of the language. such as 
  At noon in a day before summer,
  People go to a park,
  Play the guitar,
  Lie on the grass,
  Eat apples there.
This is not a great example (I know), but people can make these wordplays in Twitter, because unlike Facebook which hides a part of a long post, Twitter doesn't fold the posts and shows the whole post in a glance.

Even though these days there are no big growth of user size in Twitter and young people prefer LINE and Instagram, this social network has still vigorous presence in social network in Japan.


Reference:
http://www.emarketer.com/m/Article/Japan-Sees-Surge-Instagram-Users/1016576
http://www.humblebunny.com/japans-top-social-media-networks-2018/
https://kotaku.com/twitter-ceo-seems-unaware-of-japans-most-famous-twitter-1820703599