counter
Seoi-nage countered by Ura-nage
Against a shoulder throw that turns in a fraction slow, the defender clamps the attacker's trunk, drops their hips, and bridges backwards, throwing the attacker over their shoulder. A heavy fall to give and to take; drill it slowly and with crash mats before ever using it live.
No demonstration linked yet, and this is one of the places footage helps most. Know a good one? Suggest a video.
Each technique's own page carries its full narration, key points and how to receive it; follow the links above.