So when the scabbards attacked kaido, kaido stated that they used "Oden's Ryuo". The phrasing of this is very important. They didn't just use Ryuo, they used Oden's ryuo.
Contrary to popular belief ryuo isn't innately advanced CoA. Barrier is advanced, but barrier isn't the same thing as Ryuo. Luffy was able to use Ryuo to some degree when he clashed with big mom in udon. His ryuo, however, wasn't strong enough for him to create a barrier. Ryuo is rather simply the ability to flow haki. Every haki using swordsman does this, even tashigi and helmeppo. It is not innately advanced.
So again, when the scabbards attacked kaido, they were using very high tier haki. As kaido said, it was Oden's ryuo.
I think this is especially surprising given that someone as weak as kinemon was able to do this. Not to disrespect kinemon, but the guy was always portrayed as weaker than Luffy and Zoro, even back at punk hazard. He got cut by law and his portrayal in dressrosa honestly wasnt that great. So how did he do this?
I do not believe for a second that any of the scabbards actually have Oden's tier of haki. After all, Zoro was the first person to wield enma since oden. this wouldn't make sense if the other scabbards had Oden's tier of haki. So what could this be?
I think it ties back to their war cry, "sunachi". A cry that means to surrender all else and put your life into your attack. the scabbards have said time and time again, that this was a suicide mission, a last stand. I think what the scabbards are doing might be similar to gon in hunter x hunter.
I think that they are literally sacrificing their lives in order to artificially boost their haki for a temporary period of time. Since ryuo is about control over one's haki, this could be possible. Maybe if you have enough control over your haki, you can possibly gain access to this technique.
Overall I think this is the best explanation for what the scabbards are doing. It will allow them to actually fight kaido and deal damage, which will ultimately allow luffy and the others to win this war. However due to using this much haki, they will eventually either become crippled or outright die.
I think it might be possible that the "incurable disease" that Roger had was a result of Roger using this technique against Rocks, and that Luffy will eventually need to use this technique against blackbeard in order to surpass him. However unlike roger and the scabbards, Luffy won't die because by that time, Chopper will learn of a way to cure the disease caused by haki overuse.
Contrary to popular belief ryuo isn't innately advanced CoA. Barrier is advanced, but barrier isn't the same thing as Ryuo. Luffy was able to use Ryuo to some degree when he clashed with big mom in udon. His ryuo, however, wasn't strong enough for him to create a barrier. Ryuo is rather simply the ability to flow haki. Every haki using swordsman does this, even tashigi and helmeppo. It is not innately advanced.
So again, when the scabbards attacked kaido, they were using very high tier haki. As kaido said, it was Oden's ryuo.
I think this is especially surprising given that someone as weak as kinemon was able to do this. Not to disrespect kinemon, but the guy was always portrayed as weaker than Luffy and Zoro, even back at punk hazard. He got cut by law and his portrayal in dressrosa honestly wasnt that great. So how did he do this?
I do not believe for a second that any of the scabbards actually have Oden's tier of haki. After all, Zoro was the first person to wield enma since oden. this wouldn't make sense if the other scabbards had Oden's tier of haki. So what could this be?
I think it ties back to their war cry, "sunachi". A cry that means to surrender all else and put your life into your attack. the scabbards have said time and time again, that this was a suicide mission, a last stand. I think what the scabbards are doing might be similar to gon in hunter x hunter.
I think that they are literally sacrificing their lives in order to artificially boost their haki for a temporary period of time. Since ryuo is about control over one's haki, this could be possible. Maybe if you have enough control over your haki, you can possibly gain access to this technique.
Overall I think this is the best explanation for what the scabbards are doing. It will allow them to actually fight kaido and deal damage, which will ultimately allow luffy and the others to win this war. However due to using this much haki, they will eventually either become crippled or outright die.
I think it might be possible that the "incurable disease" that Roger had was a result of Roger using this technique against Rocks, and that Luffy will eventually need to use this technique against blackbeard in order to surpass him. However unlike roger and the scabbards, Luffy won't die because by that time, Chopper will learn of a way to cure the disease caused by haki overuse.