Writing from the road.
There’s actually no reason for a Japanese warrior to carry a katana unless he is supposed to be a member of the Samurai class. Female members of the Samurai class did not carry a katana at all, though they did have weapons training and carried a wakizashi.
Not all Japanese warriors were samurai and so not all of them carried katanas, there are quite a few martial styles devoted to subverting and stamping the samurai (or wandering ronin bandits) into the ground. Not all Japanese martial forms were meant for the Samurai. Karate, for example, isn’t part of the distinctive sets of martial arts that come down out of the Samurai training set. (Judo and Jiujutsu do, that’s why some of the more traditional training dojos teach their students to fight with a bokken, the wooden training version of the katana. It’s arguably more deadly).
If it’s a modern katana then the cryo forging, high quality steel, and a carbon fiber weave in the sword make for a much tougher weapon. If you’re looking historically and want to forgo swords entirely the tonfa, the sai (the Japanese variety of sword breaker), the kama, the nunchaku, and the staff are all more durable and will screw up a katana wielders day. Those weapons were all originally farming implements and they were the weapons of the peasant class (the weapons peasants weren’t supposed to own). And yes, even weapons made of lacquered wood will be incredibly hard on the katana. Plus, like the European varieties of sword breaker, the sai was designed to break the katana in two. It’s very good for that. You can dual wield all of the above except the staff, they’re short enough for it to work and are designed to be capable of melee combat against an armed opponent.
If you really want to go with a sword, then the wakizashi isn’t a bad option. It’s a good weapon and short enough that the folding technique actually doesn’t hurt it’s durability. You can also wield it indoors. It’s a weird choice for a Japanese warrior, but that doesn’t mean they were never used and that doesn’t mean they’re not a better weapon. It’s a decent short sword/long knife.
-Michi (Drive! Drive like the wind!)