I have volume 10 of the manga, bought it on Japanese Amazon. The fight starts at the final chapter of that manga, which is chapter 68. The latest 2 chapters (74 and 75) are available on this site on /G Manga Thread. But it only contains the conclusion of the character dying. Nothing about the fight.

It seems like the meat of the fight happened a few issues before, from chapters 69 to 73. These chapters are nearly impossible to find. Unfortunately, the author is currently on hiatus, and the next chapter will be the last chapter. Once that's done, it'll probably be released digitally and we'll finally be able to buy Volume 11 and see the actual fight. But that's a long time for now, so don't expect anything soon.