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what layer is this skirt on?
can there be a cutter based on this layer?
others

it seems to be on a higher layer than hana-cutters
hana-cutters cut the empress of dragons dress but not the bewere-pattern, but ringring cuts everything

As far as higher layer than hana, the strata a pose is on should be irrelevant to what layers it has any modification power on. For example the Foreground cutting dresses in Verhakuma and Reikalusi can cut foreground layers despite being on a lower strata than the foreground items they cut. So what actually matters is what layers it has cutouts on not what layer the skirt pixels themselves are.

That said, the RingRing does seem to cut a different range of layers than other hmm, I suppose for this type of item I personally think of them as reshapers, clothes that make other clothes fit them [ex: Cozy Mori skirt, Bearly Blushing dress] though most layer over rather than under. Though in RingRing's case it ignores many shirt/dress layers and goes for jacket/coat layers instead. Which since it does layer under dresses makes for some bolero possibilities, even with dresses slimmer if disguised as part of a bustle..Hrm well I don't have a big list of reshapers, they're fairly common but minor, but I don't know of any that work quite like this one does [layers under much and cuts a wider range]. Actually.. speaking of Crown Jewels, the skirt cutter does share some of the layers it cuts as it does remove the flowers from the Crown Jewels dress from where it's cut. Though it's hardly usable in the same way due to the other layers it cuts as well.