第四教 · Dai Yonkyo
Tani Otoshi 谷落
Valley Drop
Mechanic
Tori slides a straight leg behind both of uke's heels and drops their whole body backward alongside, so uke topples over the leg like falling into a ditch that opened up behind them.
Analogy
One kid quietly kneels on all fours right behind someone's knees while a second kid gives a gentle push from the front. The victim tips straight backward over the crouched kid, arms windmilling, into the soft grass.
Why it maps
The crouched body is tori's extended leg, a solid bar behind the knees, and the push is the backward kuzushi that leaves uke nowhere to step.