Nikajō with foot trapping

Nikajō designates the second principle and corresponds to the second kajō, which, in Daitō-ryū Aikijūjutsu, are technical classification categories. This particular principle is known as Nikkyō in most modern Aikidō federations.

This is a translation from the description of the technique from the Budō manual :
"Control the opponent’s right hand as though entering inward toward one’s chest. Then retreat further to the rear, pull the opponent down, sit at the opponent’s right side, and control the opponent’s right arm using both hands. Thereby twist the opponent’s right arm. Proceeding to Figure 24, control [the opponent] according to correct method."
These photographs are particularly interesting because they show O'Sensei stepping on Uke's foot while performing the lock (Figures 22-23).