Judging from your sig, it looks like you're just trying to start another "JPOP IS SO MUCH BETTAR THAN KPOP" thread... but anyways.
Personally, I think there's too much kpop in Japan, and not because I'm a jpop purist or anything like that. I'm just getting really tired of my favorite kpop artists debuting in Japan. I mean, all they ever do at first is release Japanese versions of their Korean songs, so it's like... there's no new music to look forward to when they go to Japan. And not only that, but 90% of the time, their Japanese is TERRIBLE. I mean, in Dara's Japanese Hate You teaser, I would NEVER have been able to tell what she was saying if not for the subtitles on the video.
I got into kpop because it was just fresh, fun, catchy pop... Which is why I've been drifting away from jpop because after 2005-2006 it kind of fell into a slump. So when kpop artists go to Japan, for me it's kind of like, you're going to the place I've been trying to get away from musically.
And also all the Japanese activities really take away from their Korean releases. I swear, I've ignored kpop for like a year because I got too lazy to keep up with everyone's releases, and now that I'm coming back to it, I've realized... all my favorite artists have released like only one thing in the past year, when they used to release a ton before going to Japan.
Anyways tl;dr I would like if Korean artists stayed in Korea and Japanese artists stayed in Japan because personally I like jpop and kpop for totally different reasons and don't want them meshed together, not because I'm one of those people who thinks "OMG KPOP ARTISTS NEED TO GTFO BECAUSE JPOP IS SO MUCH BETTER" or whatever.