In chapter 912 we see Luffy decides to go looking for a doctor as well as food and water in order to repay Tama, and Hitetsu has him change into a kimono.
Luffy decides to take a sword with him to make him look like a samurai, but Hitetsu tries to stop him, revealing that it is the cursed O Wazamono-grade sword Nidai Kitetsu that his ancestor Kotetsu had made. Luffy does not care, and races off with Tama despite Hitetsu not wanting the sword’s curse to harm Tama.
Basil Hawkins then comes to confront Luffy and Zoro as they reunite, and the two of them prepare to fight.
So, Luffy is carrying the cursed sword around and is preparing to take it out to fight. I believe during his 2 year training with Rayleigh, he would have been trained to an extent in using a sword.
Luffy may not be as good as others but I believe that Rayleigh knowing that they may enter Wano and also being a swordsman himself, would have trained Luffy in using a sword somewhat. We may see Luffy show these skills in this arc which will also add to his arsenal of powers. I believe we will see Luffy use a sword and show some hidden abilities we never would have thought he had. Thoughts?
*Theory by Strawhats360