Muzan Kibutsuji is over 1000 years old
As the progenitor demon in Demon Slayer, Muzan Kibutsuji is over a millennium in age. While his youthful looks conceal his true age, he is confirmed to be well over 1000 years old by the end of the series.
Piecing Together Muzan‘s True Age
In flashbacks, we see a young Muzan before he became a demon. Though his human age is never specified, he appears to be in his late teens or early 20s. After turning into a demon sometime in the Heian period (794-1185 CE), he maintains this youthful visage for centuries thanks to a special medicine.
According to Dr. Tamayo, Muzan ages dramatically after being exposed to her anti-demon potion:
It is revealed that Tamayo‘s drug had an aging potion mixed in along with the Demon antidote. Due to this, Muzan has aged 9,000 years within the span of three hours.
Accounting for these extra 9000 years by the end of the series, and given he was already over 1000 years old, a modest estimate would put Muzan at around 10,100 years old by the finale.
Muzan‘s Age Over Time
| Year | Age |
|---|---|
| 1185 CE (turns into demon) | Early 20s |
| Final arc (~1914 CE) | 1000+ years |
| After aging potion | ~10,100 years |
So in summary, Muzan was in his early 20s when he first became a demon, lived for over a millennium while retaining a youthful appearance, but experienced rapid aging directly leading up to his death to reach an age over 10,000 years old!
Muzan‘s Age Compared to Other Demons
Most demons in the series have lifespans numbering in the hundreds of years. Here‘s how some of the longest-lived compare:
- Kokushibo: ~300 years old
- Akaza: 113 years old
- Doma: ~500 years old
As you can see, no other demon comes close to Muzan in terms of raw age. After all, he is the very first demon, with all others having been created by him. His millennium-long existence is a testament to his power.
Interestingly, despite living for centuries, some demons like Akaza retain a similar physical age to when they first turned. In contrast, Muzan‘s rapid aging highlights his weakening in the face of the demon slayers.
Theories Around Muzan‘s Age
Some fans speculate that Muzan‘s 1000+ year lifespan could be related to the conditions around his turning into a demon.
In his backstory, we learn Muzan was born with a feeble constitution, constantly on the verge of death. It was only after intense determination he survived long enough to be administered the demon conversion elixir.
This earlier struggle could have imbued him with a powerful drive to cling onto life at all costs. In forcing his ailing human body past its limits, he gained an extraordinarily long-lived demon form.
Additionally, as the first demon, the potency of the elixir he consumed may have granted him superior longevity compared to those he later administered it to. With no precedents for comparison, 1000 years could be the upper limit for a demon‘s natural age.
The Significance of Muzan‘s Age
Regardless of open questions around his past, Muzan‘s actual age being over 1000 years carries important meaning. His existence since ancient times signifies the persistent threat demons pose to humanity in the series.
Muzan avoids death for millennium, appearing ageless, and continues to slaughter humans without end. Only through the demon slayers‘ heroic journey and Tanjiro‘s determination are the shackles of his evil finally broken.
With his rapid deterioration and death at well over 10,000 years old, his unnaturally long lifespan comes to an end. This marks the turning of a page in history – bringing new hope that the age of terror under demons has finally passed.
