It is all about money.
The Japanese market is very lucrative, and the Korean music industry is using a good window right now to gain a lot of money.

For the most part, the only "western" artists that get released in Japan are major-label acts (mostly pop, but some rap)
Unless the band or artist is part Japanese, less popular artists are unlikely to get released in Japan.

I personally think that the Korean music "invasion" is a little half-assed, because so far none of them have released original songs, only Japanese versions of their Korean hits.

I also feel like these Korean acts might discourage Japanese acts. For example, Korean girl groups might become so popular that they'll discourage Japanese girl groups (which is already hard enough because of groups like AKB48).

Specifically, groups like 4minute are basically sapping sales away from groups like dream (they are both very similar IMO).

Are there any non-Johnny's boy groups other than Tohoshinki? Sure, but they are absolutely unpopular, whereas 3/5 of Tohoshinki can release an overpriced CD of 4 songs and still make it sell like crazy.

On the other hand, more "legitimate" Korean singer-songwriters/groups like Wheesung, Epik High, or Clazziquai Project have yet to debut or (in Clazziquai Project's case) find success in Japan.

I hate how idols rule the music scene.

Japan holds the 2nd largest Market in the world. Korea's music industry wants to expand their sales. It's not only Korean artists but also other foreign artists from the West. Kpop is just a trend. Jpop may be discreet but it never fades.

Quote:

i totally LOLed @ this.. of course rather than to promote their own culture, music and tourism,..
its because of

MONEY

I think it's because for some artists there exists a tight competition between Korean artists in their motherland. For some BIG artists in Korea, they venture to Japan in other to expand their stardom even further.

I still don't know the reason why Korean singers enter the Japanese market. Tohishinki is by far the best selling Korean artist in Japan, followed by BoA.