Indeed

wakizashi parts can be obtained but it is extremely tedious where you have to dismantle and craft an absolute ♥♥♥♥ ton of wakizashis just to get just one single part. I've went my way to try and unlock every weapon part and did just that except for the wakizashi due to the amount of parts you have to unlock. The higher the tier, the faster you can unlock and you can't skip tiers so you will be stuck at tier 1 for a long time and getting to tier 3 from tier 2 is also just as long. Not only that, once you reach the higher tiers, you'll need to use better metals and usually that is the most tedious part as you will need 20 charcoal to go from crude to tamahagane. Getting metal is not really a problem since you can just smelt all the weapons you get from fighting but charcoal is required for pretty much everything so you will need a LOT of charcoal. That comes with its own problems such as weight if you plan to smelt on the move or if you already have a sizeable army, trying to focus on just smelting will bleed your money since you will spend years trying to complete the parts. Only way to really focus smelting imo is just to get a bunch of money (50k+), disband your army, make sure to have a few companions to help with smelting and producing charcoal, stay in a settlement that has a village with hardwood production nearby so you can purchase them in bulk and at a cheaper price. Even then, I do not recommend trying to unlock tier 5 wakizashis, just move on once you have unlocked everything else and made a legendary weapon of your choice.