Uchi-mata-makikomi (内股巻込), the inner thigh wrap-around.

Nage-waza (throwing techniques), Yoko-sutemi-waza (side sacrifice 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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Uchi-mata finished by wrapping: tori enters as for Uchi-mata but traps uke's arm across their shoulder and rolls with them rather than lifting them clear. A Kodokan side sacrifice, and the version most often seen when the entry is deep but the lift is not there.

Step by step (standard right-handed form)
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1. From a right-handed grip, turn in for Uchi-mata, your right leg swinging up between your partner's thighs.
2. Swing your right arm over their right arm and clamp it against your shoulder and chest.
3. Keep turning to your left, so your back is fully across their front and their arm cannot escape.
4. Continue the rotation and fall to your left side, wrapping them over your body as you go.
5. They land on their back and you land on your side beside them; turn straight in to a hold.

Key points
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1. Enter as for Uchi-mata; the leg still lifts
2. Trap the sleeve arm over your shoulder before you fall
3. Rotate as you land, so they go over and you go through

Receiving it
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The entry feels like Uchi-mata, but instead of a lift your arm is trapped and the whole thing rotates downwards. You land on your back or your side, with one arm pinned. Chin tucked, free arm slapping, and stay loose: fighting the wrap on the way down is how shoulders get hurt.

Reference pages elsewhere
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Uchi-mata-makikomi on the IJF technique reference (International Judo Federation): https://judo.ijf.org/techniques/Uchi-mata-makikomi

From Waza Book: https://wazabook.com/techniques/uchi-mata-makikomi/