Step 4-6 of Heian Nidan is the second cluster: double-block to the right this time, cross up the forearms, then an apparent hammerstrike to the right with the right hand. If you have not read the discussion of Step 1-3, you'll need to start there.
The shoulder lock applications of Step 1-3 apply here with equal force, but in mirror image.
The Tachi Dori applications of Step 1-3 can be applied here in mirror image, but we can also take Tachi Dori in a new direction now. We stole a katana from our first opponent in Step 1-3. That sword is in our left hand as we start the same series of movements on the opposite side. How might that enhance our interpretation?
On your right, a samurai has raised his katana overhead for the vertical cut at your head. For Step 4 (double "block") you can shift in (tai sabaki) to get inside the sweep of his sword. Use your vertical right forearm to bat his hands away from you (to his right). Your left hand runs your sword into his abdomen.
You want a quick kill here, so probe for the major blood vessels that lie against the spine. It isn't difficult to use your right hand to snatch his sword away (step 5), and once you have control of it, you can slash back to the right and cut his throat (step 6).
Now you have two swords, one in each hand. The opens up the possibility that we are about to explore Nito Ryu, the two-sword variant of Kendo.