Reference: The "Lopresti Spin," Paul Lopresti, personal instruction.
Also, "Ude Gatame pin," demonstrated as part of "Te Yoko Nage," technique 2-16 of George Kirby, Black Belt Budoshin Jujitsu, Volume 1, Panther Productions, 1992.
Step 2-5 of Empi finds us rising to a standing position (step 2), stepping out to the east with a downblock (step 3), and pivoting back to face north with a hook punch (step 3). Then we step forward (north) in a front stance and downblock (step 5).
I know a move that fits these gestures pretty well, and is very appropriate as a follow-on to the sode otoshi throw in step 1. I call it the "Lopresti spin" because I learned it from Paul Lopresti, one of the leading lights of the karate jutsu movement. Paul and his friends put on a very exciting seminar every year in Atlantic City.
The Lopresti Spin is almost a magic trick. Students love it, and it is very practical. Take hold of your partner's right arm and, using any of a wide selection of throws, take him down on his back. You'll be in handachi position, just like step 1 of the kata. You still have hold of his right wrist, preferably with both hands.
He will attempt to escape when he hits the floor. Stand up and pull his arm up straight (step 2), partly to get transfer his weight to the small of his back so you can use it as a pivot. Pull his arm strongly to your right (the gedan barai of step 3), making him spin 180 degrees anti-clockwise on the floor. When he has completed the half-turn, pull his arm directly toward your hip (the hiki te of step 4). This makes him flop over on his belly. His arm naturally locks up into an ude gatame pin as a result of the spin. This pin locks the wrist, elbow and shoulder all at once. To apply pain compliance, push his captured arm away from you (the gedan barai in step 4), locking his shoulder.
Note that this trick is very difficult to do if your partner lies limply on the floor. If he makes the slightest effort to sit up, however, you can spin him into the compliance hold in less than a second.
This interpretation does not completely account for the kage zuki in step 4, but if your hang on to his wrist with both hands during this maneuver, you'll find your left arm in kage zuki position at precisely that moment. This satisfies the Shadow Principle. Perhaps that is sufficient.