Obi-tori-gaeshi (帯取返), the belt grab reversal.

Nage-waza (throwing techniques), Te-waza (hand techniques).
Required for: 3rd Dan (black belt, British Judo Association); 4th Dan (black belt, British Judo Association); 5th Dan (black belt, British Judo Association).

About
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The answer to a partner bent forward and defending: tori takes the back of their belt, lifts them off their base and turns them over backwards. Recognised by the Kodokan beyond the Gokyo and common in contest, where a bent-over posture invites it.

Step by step (standard right-handed form)
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1. Your partner is bent forward, defending, their head below your chest.
2. Slide your right arm over their back and take the belt behind them, thumb hooked under it.
3. Step in close so your hips are under theirs and your knees are bent; keep your own back straight.
4. Straighten your legs to lift them off the mat, and at the same moment turn to your left so they rotate rather than simply rise.
5. They come over and land on their back in front of you; lower them with the belt hand rather than dropping them.

Key points
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1. Take the belt at the BACK, over their spine
2. Lift with the legs and hips, never the lower back
3. Turn them as you lift; a straight lift only stands them up

Receiving it
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A hand hooks the back of your belt while you are bent forward, and your feet leave the mat before you can straighten up. The fall is backwards onto your back, and you cannot step out of it once the lift starts, so tuck your chin hard, keep both arms ready to slap, and stay heavy rather than fighting the turn in the air. Build this one up gradually with a partner you trust.

Reference pages elsewhere
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Obi-tori-gaeshi on the IJF technique reference (International Judo Federation): https://judo.ijf.org/techniques/Obi-tori-gaeshi

From Waza Book: https://wazabook.com/techniques/obi-tori-gaeshi/