Marie's world was polluted during the ancient human-demon war. The Mana Collapse. "Even those foul smelling meats and vegetables are tainted by it's lingering effects." I wonder if this just effects the taste of their food; or if there are also other negative effects. Like maybe food is less nutritious.
If there is a way to cleanse this pollution, you'd think that Wridra would make that a priority, and have mentioned it much earlier. Especially since she's tasted unpolluted food from Japan. Making food taste better for an entire world, would be a very good long term goal. Also, don't ever take Marie and Wridra to America. Most of our food is poisoned with glyphosate (wee killer), emulsifiers, preservatives, flavor enhancers, and food dyes.