第三教 · Dai Sankyo
Hane Goshi 跳腰
Spring Hip
Mechanic
Tori tucks in close with one bent, springy leg pressed across uke's thighs and the hip loaded under uke. Then the leg snaps straight with a hop ('hane' means spring), bouncing uke up off the coiled leg and over.
Analogy
You bounce hard on the playground's spring horse and squash the fat coil underneath you flat. The coil is not interested in staying squashed. It snaps straight, pops you off the seat, and sends you over the handle in a slow forward roll.
Why it maps
The coil under the seat is tori's bent, loaded leg, and its release throws you upward off it while the handle in front becomes the low edge you rotate over.