OK, get out your notebooks, Ishiura’s teaching class today. This is a prime example of a picture-perfect shitatehineri (twisting underarm throw).
Step 1: Underarm grip. Left side. As far around the back as you can reach.
Step 2: Front-belt grip. Right hand. 180 degrees from your other hand.
Step 3: Pull with the left, push with the right. Like opening a giant jar of pickles, except the jar is your opponent and let’s not take the pickles metaphor too far, ‘kay?