Wow this is good news... I do hope they get to pocket some of the fees though.. DSP known to be kinda stingy?
On the other hand, i think they really appeal to a wider audience of japanese due to their casual and familiar image... All of them try to speak japanese on all the shows which appeared so far. They also had been able to interact freely with the hosts (Shakeburi007?) on the shows they had been on, pretty much like any japanese artist without need of the translator's voice over. I am sure this was why they were chosen as the Japanese take a lot of pride in their language and see this very positively.
Overall I feel they have made a pretty deep impact in the Japanese for such a short period of time. From what I see, Japanese media has pretty much included Kara as part of their music industry and there are substantially quite a number of news and reports on them happening constantly.
The only drawback is that they have to sacrifice some marketing back in Korea and have to work much harder now. Still, they appear on regular programs (Hara, Nicole , Gyuri) and thanks to it we can see them weekly (HAM AND JING NEED A REGULAR PROGRAM!).