In order to fight the secret boss of the game, you must first obtain the party member after beating the volcano. Following that, fly to the cave right next to the left of the beginning of the game. The secret boss is at the end of the hallway and It requires training, because it will kill every party member on it's fifth or sixth turn.
Cthulhu Saves the World Secret Boss
What do these eShop changes mean?
A frustrating way to start a game.
Get your special suit.