Twitter has become so big & popular in Japan that BIGLOBE has decided to start keeping monthly tabs on what Japanese people are tweeting about, & are sharing the results for all to see. What's really interesting is seeing how popular Tweets about anime & manga are ranking really high up there. Then again, it's always the nerds (or in this case otaku) that are the early adopters of new technology, so perhaps it's not that surprising.
Among the most Tweeted about words that related to anime & manga for the month of April, "K-On!" topped the list as the fifth most tweeted Japanese word. That shouldn't come as too surprising considering how gigantic that series is, but the sixth most Tweeted word should be much more surprising- "Main," as in in "Cookin Idol Ai Mai Main!" That's right, out of all the anime to talk about in Japan, "Cookin Idol" was the second most popular. Talk about crazy, huh? Rounding out the top 10 words list, "Ayu" (as in seiyuu/singer Ayumi Hamasaki) came in at eight, while "Precure" ended up at the ten spot.
A separate top ten category was created for hashtag topics. Again, "#k_on" topped the list for things relating to anime, coming in at third place. It then repeated it's result with "#keion" coming in at number six. The new Key series "#AngelBeats" followed at seventh place, & "#arakawa_ub" (for the Arakawa Under the Bridge anime) came in ninth. Rounding out the list again was "#Precure" coming in at tenth.
Source:
http://www.animenewsnetwork.com/news/2010-05-10/japan-twitter-ranking-april-2010/k-on-precure-more