I'm kinda scared to ask, but what's the flavor of the bottom layer?

Considering the cook? Poison.

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Considering that Medi even left her lilies of the valley at the top as a decorative item... yeah, even in the first layer this smells as poison

Medicine and Mayumi couplet? Considering Mayumi is arguably a type of doll.(Clay doll.) And she's obviously immune to Medicine's poison, could be an interesting pairing. Also a chance for maybe Medicine to settle her grudge.