Kanji
If it means anything, there's a Yu-Gi-Oh Card that uses the kanji "浮幽" called "浮幽さくら" (fuyu sakura). For reference, the character on the card is a ghost girl with a scythe. A pun is made of it as "浮幽" (fuyu) is a homophone of the Japanese word for Winter, but the kanji used supposedly reads "Floating/Drifting Ghost". So it sounds like "Winter Cherry Blossoms" but actually says "Floating Ghost Cherry Blossoms". When the card was released in English it was written as "Ghost Reaper and Winter Cherries."
With this in mind, is it possible that there's a connection between this world's name and this random Yu-Gi-Oh card?. It may be possible that this world has a similar pun, with "fuyukai" being a homophone of the Japanese word for discomfort/unpleasentness.
I'm tired so sorry if this doesn't make much sense, but I'm trying to spark up some ideas of how we could work out this world's Japanese name.