Erza Scarlet with her legs spread using something like the grip or sheath of a sword to masturbate her ass with one hand while fingering herself to orgasm with the other.

Erza in this outfit (leave the thigh highs on)

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Nico Robin (post time skip) and Rebecca (One piece) sharing a double dildo. Both are dressed in sexy cat girl outfits.

Stockings/thigh high boots on one or both characters. Nothing with too much fur, mainly just the ears and a few other small add ons.

some examples:

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