Sumiotoshi is accomplished by Tori stepping his left foot (or right foot) beside Uke's right foot (or left foot). Using his body movement and both hands Tori puts Uke off balance to his right backward (or left backward). Then, Tori pushes Uke up and throws down or similar to this type of techniques.
Uke falls backward in a big circular motion with his heel as the pivot point.
The key point of this technique is Uke's inability to put his weight on his left foot and his weight shifting heavily to his right foot, causing him to lose his balance. To accomplish this, Tori needs well coordinated body movement and work of both hands.
Tori & Uke hold each other in right natural posture. Uke steps back to pull Tori. The moment Tori steps his right foot forward, Uke executes left Sasaetsurikomiashi. Tori perceiving Uke's attempt as Uke stands on his right leg, moves his right foot close to his left foot to support his body firmly as he steps in his left foot close to the outside of Uke's right leg to become a defensive posture. Then, Tori lifts his right hand (while gripping Uke's left collar) and pulls his left hand down to put Uke off balance to his right backward. Tori throw down Uke as explained in type 1. The key point of this technique is Tori must perceive Uke's move, such as Uke's execution of Sasaetsurikomiashi (standing on right foot and left foot is off of the ground). Therefore, timing is very important. The following can be similarly changed to Sumiotoshi: All throw that start with Uke standing on one leg, such as Hizaguruma (foot technique), Haraitsurikomiashi (foot technique).
2. Dodging Uke's Uchimata (foot technique) by stepping behind Uke's body and executing Sumiotoshi.
When Tori steps back his right foot, Uke executes right Uchimata by swinging up his right leg. Tori jumps in with his left foot far behind Uke's supporting left leg and he twists his body to the right and steps back his right foot toward his left heel to dodge. Uke's right leg floats in the air and loses his balance since his weight moved to the outside of his left foot. While Uke's body is off balance, Tori throws Uke straight down with both hand. Sometimes, Tori covers Uke with his body to throw down.
When Uke uses the following techniques, Tori is able to dodge and execute Sumiotoshi.
Hanegoshi (hip technique), Haraigoshi (hip technique), Seoinage (hand technique) Tsurikomigoshi (hip technique). When Uke tries to execute any technique, but loses his balance for some reason, Tori can throw Uke down backwards. This is still considered as Sumiotoshi. When Tori quickly twist his body and uses his left foot (or leg) to sweep (or hook) Uke's left supporting leg, it is called Uchimatagaeshi. When Tori twists his body to his right (opposite movement of Sumiotoshi) and dodge Uke's right Uchimata to throw, it is called Uchimatasukashi.
Sumiotoshi: Make Uke's body off balance to his right backward (Uke's right heel) and throw down in the direction of Uke's right heel.
Ukiotoshi: Make Uke's body off balance to his right forward (Uke's right toe) and pull down or push down to throw in the direction of Uke's right toe.
It is easy to understand the difference between these two techniques since the direction of putting off balance and throwing is opposite.