Ah, OK! Thanks for the info. on that.
Actually the katana, much like the rapier is a sidearm.
Again, I suspect that unless the fencer was to get in a really well placed thrust to something vital, a rapier simply does not have the stopping power to stop someone with a katana from cutting the fencer fatally.
With proper technique, a rapierist can prevail. Although we have no historical accounts of rapierists versus longswordsmen, sparring shows that it can be done. Since katana and longsword technique are so similar, it's not that much of a stretch at all. IIRC, there are some accounts of Portuguese rapierists duelling Samurai in Japan, and proving to be their equals in prowess. Also, Portuguese trading ships had to fend off attacks from Japanese pirates, some of which had former Samurai among the crew, serving as marines, I guess. It's not only the weapon, it's not only the art, it's the person using the tools to the best effect.