This chapter also proof two things:
- Oden learn Ryou most like after travel around the world, my bet is on Roger crew since he doesn't know back then Ryou,Oden most like learn Ryou from Rayleigh and Roger.
-Normal Hardening on the swords like we see of Zoro and other characters aren't Ryou too, since the scabbard didn't know back then ryou yet still had most like haki.
Let see how Ryou looking like in this chapter when swordmens and Gunmens using it.