Edit: Didn't think I had to explain this because it's very obvious to me, but I'm kind of a lore geek so in case it's not common knowledge...
1) Foxfire (Kitsune-bi) - By rubbing their tails together, a kitsune can make lightning or fire. The kitsune can also, to a small range, breathe out fire. Kitsune can also make small 'fox lanterns', by producing small balls of fire to float around them, and guide their way. This fire can be used as a weapon, or as a toy.
2) Foxfire - the term for the bioluminescence created in the right conditions by a few species of fungi that decay wood.
My thoughts were kitsune playing with foxfire (the burny kind of fire) could be responsible for foxfire (the glowy mushroom kind), and that while they're playing with the burning foxfire they could singe the mushrooms and cause them to glow the way they do. That *is* a fireball coming from the dude on the left. It's just green. :P
For those who missed this in chemistry:
How To Make Green Fire
How to Make Green Fire from Materials Found at Home