As Kamui you generally want to get knockdown into safe kunugi or oki as much as possible.
Unless you're going for the kill you should just stick to doing the uruma loop efc combo which allows for better positioning and oki.
Just do the standard uruma loop as it works on all characters and arcana (except earth) in and outside the corner, although you might have to add some delay on certain characters. 41236X EFC 5A 5B 41236A 5A 5B 41236A into ender of choice (eg. Arcana Eclipse, 5B/5C otg 22A, extra rep of uruma)
For combos outside of ef (when you don't have access to it), my go to bnb is 41236X 6D 3B 214B~C 3B jA jB djA djB djC j421C and if you want to spend the meter you can add j236AB or cancel into arcana super for oki. The 3B 214B~C will not work on some characters (Scharl, Lieselotte) and will need to be adjusted to 3B 214B 5A.
For that same non efc bnb you can omit the air combo and just go for uruma ender for better oki. 41236X 6D 5A 5B 214B~C 5A 5B 41236A/B here you can either do 22C 5A otg into immediate mixup (dash up tk seizan or kagetsuki) or, if you don't want to spend that huge chunk of health, 5B/5C otg 22A for safe kunugi setup.
As much as I hate to say it, as a long time Kamui user, if you're using any arcana that isn't Earth BC SUPER may not be the most optimal confirm you can do if you hit at max range assuming that you have extend force ready. Off max ranged 5B 5C you can EFC 66 5B 5C 41236C into Arcana Eclipse, this is a more optimal confirm for 5BC as it gets you more damage and better positioning just like any other uruma ender.