They're the brown haired person wearing blue clothing. Also the ending in the demon is just a placeholder ending because they appear in the trailer for The Winds of Basidia which will be a full game set in the same world but after the events of The Snow of Basidia.
Also if anyone survives it will probably be the protagonist who has to travel the world finding ingredients to create a cure while finding and destroying the source of the mushrooms and killing any Mushrooms Zombies they come across.. but that's just my guess as to what the game will be about.
Here's were you can watch the trailer for The Winds of Basidia since it's not on Youtube - (4) Modus Interactive on Twitter: "🍄The Winds of Basidia🍄 It's still a long way off but you should be excited for what Bryce and I are cooking up here!" / Twitter