In Chapter 1053, Ryokugyu, whose real name is Aramaki, is fully seen for the first time.
Looking closely at his pants, I can see the sword is inserted from the inside and sticks out from the outside (is that why his pants are ripped?) so its not really attached to the belt like some of us have assumed. Let’s look at the sword now:
Without a doubt, there is no scabbard/sheath here… it looks too sharp and edgy for that to be possible. This is a blade, as you can clearly see the hamon (hardened outline) in the middle (yellow).
Here is another black blade (Shusui) for reference and comparison:
Or perhaps we are reading too much into this and he just coated his sword with the usual Armament Haki black hardening…?