Sasuke's Rinnegan Ability.
From what I came to know from today's chapter,
Sasuke's Left eye's ability is "SHIFTING". At first, I thought, it's an ability of swapping because of this vvvv
But I was wrong. He can not only swap himself with something else but can also shift himself from one place to another. And this is shown here vvvv
MADARA used the lightning jutsu. Sasuke just activated his ability.
MADARA aimed the lightning in his other hand towards Sasuke. But Sasuke shifted himself from that place to some where else.
But, similar to how Madara can use "Limbo" for a particular interval of time as well as he can activate it after a particular interval of time, there's also limitations to Sasuke's Left eye.
Sasuke's left eye's ability can ONLY be used within a certain RANGE and also takes a certain amount of time to be used again.
And that's how he shifted his sword with himself when Madara approached him. But it seems that with this ability he can even use/apply force on the objects he can shift.
When Madara approached Kakashi who was far away from Sasuke, Madara noticed that Sasuke can't do the shifting technique this far. Instead Sasuke used his speed to approach Kakashi similar to how Madara approached Kakashi with speed. But I think Sasuke actually used the ability to shift himself more close to Kakashi's location to speed up. With this , he was able to utilize his range efficiently and then he speed up to Kakashi.
In this image, you can see Madara found the weak point. Also this page showed Sasuke had to activate his ability to see whether which Madara they attacked. Means the ability was active when he used the shifting to approach Kakashi and then speed up to cut Madara.
It's more similar to Minato's Flying Thunder God Technique. Similar to Minato's technique Sasuke might be leaving some chakra (his) trails on the objects, person he touches (in the current state) and hence when he's in range with the objects, person he touched, he can swap/shift places to avoid/dodge a normal/fatal attack.
There might be chances that by further practice, Sasuke might increase his range or he haven't yet able to fully utilize his left eye's technique.
That's all. Thank You.
EDIT : A little more kind of confirmation to my theory.
When Sasuke and Naruto prepared Chidori and Magnet style Rasengan, Sasuke said Naruto to aim his rasengan at him.
And then this happened
From the look of it, it looked like Naruto and Sasuke dashed towards Madara from either sides and attacked Madara who was standing infront of them.
But from what I analyzed is that Sasuke activated his ability and shifted Madara from his previous position to in between Naruto and himself. And that's why Naruto sensed Madara's appearance where Sasuke was standing and aimed his rasengan at Sasuke in order to hit Madara who just got shifted. Even Madara seemed surprised.