1. Two people (futari) attack (gake) with ryotemochi. Sensei shows the standard form of shihonage.
2. Analysis of the possibilities if one person attacks with katatedori. Nage could just break free. If necessary, he can move Uke's arm away to the side. It is irrelevant whether Uke continues to hold on or not. Nage can take hold of Uke's wrist and thus control him. This is how shihonage emerges.
3. If two people attack, Nage must move away from the line of attack. So the second Uke is practically compelled to take Nage's second arm.
4. In the standard form of Ki Aikido, the two Uke grasp the wrists of Nage with ryotemochi from the beginning. Based on the mathematical analysis worked out beforehand, a simple standard form for shihonage against futarigake results.