Overview
The first one can be encountered in FC World B. There is a 1-in-6 chance that he will appear in the place which has its entrance surrounded by six pyramids. However, he will always appear with if Madotsuki has the Demon effect equipped. He teleports Madotsuki to the FC Basement, right next to the second FC Demon.
The second one can be found inside the FC Demon's Room in FC Basement. The Demon effect can be acquired by interacting with him.
The FC Demon resembles a traditional Japanese Oni due to his red color and horns.