Let me also tag
@Gallant and
@Zack since this might interest them as well.
You might also look to Miyamoto Musashi's
Book of Five Rings, as it is one of the few martial arts manuals that speaks frankly about practical sword fighting, and is widely published.
In literature, R. A. Salvatore's books usually have extensive combat and he is quite good at describing it.
In setting, the Ketsurui Samurai are often mentioned to have a martial arts form of their own, but that seems to be the only prominent form of martial arts. I tried to quietly correct this, once, by introducing a spear-form combat style with the Morioka Clan, and Taisho Morioka Nao, Inochi no Senshuu - the "Thousand Lives" doctrine - but that was always meant to be more of a religious exercise, too. Something like Shorenji Kempo.
I always imagined that there were many forms of unlisted martial art.
Bear in mind that any Martial art is built by repetition. Each martial art is different because the exact forms of those repetitions change or are changed by successive generations. This is especially prominent in China, and most famously, with Wong Fei Hung, or with Bruce Lee's mentor, Ip Man. Obviously, Bruce Lee might practice Wing Chun, but it might not be exactly Ip Man's Wing Chun, and so on. There end up being different schools of Wing Chun as time goes on and though there are obviously forms and tests, each practitioner is always a little different and I think that does get passed on to their successors. Therefore, you may find it worthwhile to start with something like Fred's
Sore Mai, and to create a branch from that. Sore Mai itself might be quite old, but Yuumato Ryo-Sensei's version, which he likes to call Sore Gak, might be relatively new - just based on an older martial art.
That way you might have an old "lineage", but a different form of martial art, and that could make a lot of sense in setting.
Another interesting thought is that gravity manipulation would hypothetically allow you to deliver strikes "heaven fist" style; you could manipulate your own gravity to deliver compounding force strikes from above by causing your arms (with your sword in them!) to grow heavier, or to cause yourself to 'stick' to the ground, or even slide across it, so that your balance wouldn't falter. Although I never named that style, so to speak, I always imagined that an engineer (like Yuzuki, for instance) or someone more physics-inclined might eventually develop something crude and brutal like that.