The Sumi Gaeshi is done by grabbing your uke opposite you by their clothing, more specifically below the collar. The tori then plants their foot or knee in the opposite upper thigh, taking care not to hit the groin. The user then rolls backwards using the forward momentum of the opponent to propel them forward. This can be followed up with any number of grapples, joint extensions, or choke holds.
The Sumi-gaeshi (Corner throw) consists of destabilizing the opponent in the forward direction, and then inserting a leg between the opponent's legs, dropping onto one's back, and then throwing the opponent back over one's head.
From the Kenka yotsu (Asymmetrical grips by the two opponents) stance, Tori grasps the back of Uke uniform with his Tsurite (Lifting hand), using that hand together with his Hiki-te (Pulling hand) to pull Uke forward.
At the moment when Uke balance is destabilized in the forward direction, Tori falls backward with his foot hooked in Uke crotch, and throws him over his head in a sudden motion.
Tori performs the throw by hooking the instep of his foot in Uke’s crotch, followed by an upward kicking motion.
In actual competition, this Waza is often occurs from a stance in which both combatants are sideways to each other, with both their Hiki-te (Pulling hand) free. When one of the combatants makes an aggressive move to obtain a Hiki-te (Pulling hand) grasp, the other combatant submarines feet first beneath him and executes this Waza.
The Sumi-gaeshi (Corner throw) is a Ma sutemi waza (Supine sacrifice techniques), and is which are performed while in motion.
Although it is uncommon among Japanese combatants, it resembles the “Sambo" martial arts of the former Soviet Union, and Russian and Georgian combatants, etc., are particularly skillful in its use.