Demon Slayer season 3 ended with a cliffhanger and left with an expectation of what else going to happen in the next season. Season 3 concluded with Muzan’s entry to the Ubuyashiki Estate and realizing it was a trap set for his defeat and the beginning of the war between the Demon Slayers and Demons. There are several reasons why fans are eagerly waiting for Season 4 which includes the origin of all demons and the origin of the Sun breathing.
1. The Origin of "Mark"
The Demon Slayer Mark is said to have originated during the Sengoku Era. The “Mark” that was acquired by the person will help them to unlock their true strength along with the ability called “Transparent world”. The Transparent World lets the person see through the flesh of the body. The only downside of acquiring the “Mark” is the holder will die before even reaching the age of 25. We might expect the origin of the Mark and his history.
2. Origin of Demons
Muzan was the first Demon which was revealed in Season 1 itself. The Infinity Castle arc might contain the story about Muzan’s Life as a human and how the beginning of the Demon era started. This arc might reveal the story of why Muzan constantly lives in fear of death. Unlike other demon, Muzan can’t die like decapitation. Muzan created that weakness for other demons to make them weak and inferior to him.
3. Yorichi's Flashback
Yorichi was the first person to use Sun Breathing and also the first one to create any Breathing Techniques. It is already revealed that Sun Breathing was the origin of all breathing forms. So this arc might reveal how Yorichi was able to invent a breathing form and his past encounter with Muzan. The past of Yorichi and how his life impacted Kokushibo’s life might be revealed in the Infinite Castle arc.
4. Kokushibo's Strength
Kokushibo is the only Demon that knows how to use Breathing forms and also possesses the Demon Slayer “Mark” and knows the full truth about it. The Infinity Castle might reveal how Kokushibo gained the “Mark” and his true strength which was not shown in anime until now. The Techniques Kokushibo use is far different from any other demons. He is a skilled swordsman along with regeneration ability will make him a formidable enemy for the Demon Slayers.
5. Zenitsu's Final Form
