^^ AKB48 I guess, they're as popular in japan as SNSD is in Korea.
^ couldn't have worded that better
Well besides the fact that K-pop is trendy in Japan right now, they already had a dedicated fan base in Japan, their showcase was completely sold-out even before their official debut
Also, if you watch their Japanese shows, you'll notice how most of their Japanese fans are teenage girls who look up to them and like to cosplay as them.
Plus they're gorgeous, funny, talented, and each one is different in her own way
If you try to get to know them you'll see why they're so popular
btw can we stop with the random "why is kpop popular" threads ? It only gives chances for people to make rude comments about it .. All this hate is giving me a headache