Yoki Manipulation needs yoki to work on. It's just like Yoki Sensing. A Claymore uses their yoki on the target's yoki to sense that target's yoki and thus the target. Same with all other Yoki abilities, including Teresa's and now Clare's "PYS" ability.
Also, Yoki abilities are effected by whichever's yoki is more powerful. There's no character that can use Yoki Manipulation or Yoki Control on Priscilla, because her yoki is just too powerful. We see how the Destroyer's projectiles have no effect on Priscilla, compared to Deneve and Beth (though Priscilla was never impaled by a huge projectile... they just blew chunks out of her... and out of Clare...)
Take the Pieta ABs and their Yoki Control ability. They could effect the weaker yoki Undine, the two Claymores, and even Clare and Deneve....
Until Clare and Deneve raised their yoki to 80%, at which point their yoki was powerful enough to break the Yoki Control upon their bodies.
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Dauf was obviously already releasing his yoki.
Galatea had to use verbal insults, a 2v1 combat (Clare's help), and Clare's Quick Sword to distract and dis-concentrate Dauf, in order for her Yoki Manipulation to effect him.
Whereas, Riful countered it, by motivating Dauf to fully concentrate and to use his full force (as Galatea's Yoki Manipulation wasn't very strong, it wasn't Yoki Control, like the 2 Pieta ABs had), which once he did, Galatea's Yoki Manipulation had no effect on him.
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After the trainee Awakening Twins got Miria to release her yoki and use the Phantom Step....
Raftela could then use her weaker Yoki Manipulation ability to distort Miria's senses.
Once Miria was distracted and dis-concentrating from her distorted senses, Raftela could now with her stronger Yoki Manipulation ability, invade Miria's mind, and cause the mental illusion of her beloved Hilda.