Reverse yokomen-uchi = Gyaku Yokomen-uchi in Yoshinkan term.

Possible (High Percentage) techniques to counter this action are in jiyu-waza setting:

1) Kotegashi ni (tenkan version)

2) Ikkajo/Ikkyo ichi (irimi version), for this you have to get in fast enough before the swing actually start or before the swing acheive great momentum.

3) Ushiro nage

4) irimi tsuki (shomen ate) - but then irimi tsuki is suitable as a response to anything..... see my signature.

The terms I speak are Yoshinkan, I am unsure what Aikikai call them.

Boon.