Honestly, I don't really know the whole NcSoft vs Nexon story, just what I can glean from net news sources, and I doubt that very many people outside the industry really do have the whole picture. They had done a small stock exchange and had an agreement to develop a mobile gaming platform together. At some point either NcSoft backed off or Nexon accused them of not doing enough of their part, whatever cause, their agreement crumbled.
Nexon announced their displeasure and demanded a shift in the control of NcSoft, they wanted a bigger voice than their shares really deserved. When Nexon didn't get their way, they announced they would retaliate by launching a hostile takeover of NcSoft, many folks speculate that it was really just an excuse, what they may have been trying to do was increase the size of their portfolio to become the biggest fish in the pond. Whatever the reason, it failed when NcSoft invested in yet another company, Netmarble, thus increasing their own portfolio (Value doubled in a day) and financial footprint out of Nexon's reach. Some of the NcSoft money involved came from investors that Nexon had previously thought were on their side.
In a strange kind of irony, Nexon, who is the single largest stockholder in NCSoft, also gained a boost in total value with the increase in NCSoft's net worth, but controlling interest had moved even further out of their reach.
And in a kind of "Salt in the wound" irony, Netmarble, the company that NcSoft purchased, produces exactly the type of mobile gaming software that Nexon had wanted NcSoft to develop for them when this all began. And NcSoft plans to take advantage of that, they have ₩ signs (Korean currency symbol) in their eyes and could soon be the biggest dog in mobile gaming.
There is tons of butthurt involved here, beyond normal biz relations, most of the key players were personal friends and broke into the industry together, there are family and nepotism issues with public finger pointing and snide snipes in the media.
It's probably not over yet, but unless Nexon can come up with something truly brilliant, control of NcSoft will remain out of their reach.