If you want to unlock Thunder Breathing in Roblox Demon fall, you will need to speak to an old man called Kojima inside a house located in the coast forest.
However, before you try to complete this quest, you will first need to be human, as certain steps of the quest require you to be human in order for you to complete them and get Thunder Breathing.
That said, when you find Kojima, he will give you the Thunder Breathing ability but only after completing several tasks. The first task you will need to complete to get Thunder Breathing involves getting a total of 20 soups from the Okuyia Village.
You can get the soups from the shopkeeper in the village, and each will cost 20 yen, so you will need a total of 400 yen to get them all.
If you don't have the required amount of yen, you can farm yen by slaying monsters and selling their parts or by completing the various quests in the game.
Once you have the yen, buy the soup and return to the old man in the coastal forest. The next task he will give you is to deliver a letter to a man called Maronne, who can be found inside the Slayer Corps HQ, which can be found in Corps Grove.
Look for Maronne in front of the Hotel and speak to him to give the letter to them. After this, the next and final task to get Thunder Breathing in Demonfall will require you to provide the old man 4k yen. As we said before, the best way to get yen is to slay demons and sell their parts or complete quests.
You can also sell trinkets that you can find spawning in various places around the world to get yen, and when you get enough yen, return to the old man and give him all 4k yen. After you do, you will get Thunder Breathing as a reward for completing his final task.
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