many say that oda keeping for a strong villain cuz till now zoro didn't meet one .
but I will say that oda changed his mind and want to get rid of Asura Technique , for a simple reason :
-zoro is known for 3 swords style ,
Santoryu is definition and a main figure for zoro character & as a swordsman
so if zoro has more powerful style (
Kyutoryu) that's is superior to
Santoryu this will make zoro lose his theme , he will not
Santoryu swordsman , just a swordsman who can use many styles .
that's why i think asura is no more Technique for zoro .
if oda will give him more powerful Technique then it will be with
Santoryu
...............
but maybe i am wrong cuz oda already gave sanji RS which have many Technique outside his original style .
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Kiki Kyutoryu: Asura literally meaning "
Ghastly Nine Sword/Blade Style: Asura")
Ghastly : resembling a ghost
Also kaku said illusion , so what i want is zoro using Asura (with any style he want ) without drawing his swords
similar to this