Translation
For that play which is before me I made you turn and immediately I threw my sword around your neck. If I do not cut your throat, then I am sad and foolish.
Interpretation
The play of the 7th scholar of the sword in one hand is a continuation from the elbow push made by the 6th scholar. Step through with your right foot while pushing your opponents elbow across your body with your left hand. This extra step will turn them well to the side, allowing you to get behind. Quickly step in close with you left foot. As you do so, swing your sword over your opponents shoulder and under their chin. Grab onto the blade with your left hand. You should find yourself in the position depicted.
As you swing the blade across, begin by laying the flat of the blade against your opponent. It is a little easier to grab onto, and also if you accidentally hit the chin, the blade is more likely to deflect under the throat to where you want it. Pull your hands back into your shoulders, rolling the edge of the blade into the throat as you do so. This will pull your opponent off balance as well as begin the cut.
Arc your right foot in a clockwise direction behind you and then make a volta stabile, following your foot. This will leave you facing the opposite direction to the picture. As you turn, slide the blade from hilt to point across the throat. The momentum of your turn will greatly magnify the force of the cut. You should be able to make a single slice all the way through the throat. Your opponent will collapse dead at yout feet in a tremendous spray of blood.
You can also see the application of this technique in the 4th scholar of the 3rd master of sword in two hands.