The Case Against Inuyasha Being 200 Years Old (and How Half-Demons Really Age)
In the third Inuyasha movie, “Swords of an Honorable Ruler”, it is stated that Inuyasha’s father died 200 years earlier, on the day Inuyasha himself was born, making Inuyasha 200 years old when we meet him in the series.
I understand why people just accept this as fact, but I think it makes no sense considering the information we are given in the manga. I’m going to explain in this post why I think Inuyasha is simply 65 years old (15 normal years + 50 years sealed) and why he most likely age like a normal human.
1. Canon evidence
What matters to me when analyzing the series is the author’s intent when she wrote the story. So my opinions and analyses regarding Inuyasha will always be based on the source material (the manga) and the word of god from Rumiko Takahashi herself. The movies, anime and spin-off were created by Sunrise (written by Katsuyuki Sumisawa), and thus are not canon. I will be addressing some elements from them later on to entertain Sunrise’s ideas, but I wanted to make clear that Rumiko Takahashi “supporting” adaptions does not mean that elements from these stories necessarily make sense in the context of the canon story.
There is no mention of Inuyasha’s age anywhere in the manga beyond the fact that he was sealed to the Goshinboku (Sacred Tree) for 50 years, but Rumiko Takahashi herself has confirmed that Inuyasha is mentally 15 years old, same as Kagome. The very first evidence I could find of this was in a 2001 blog post on websunday.net, where she said:
“So since Inuyasha is a half-demon, how he ages is a bit of a mystery. He was pinned [to the Sacred Tree] for 50 years, so that makes it difficult. But he was frozen for those 50 years. Emotionally, I think it would be best if he was about 15 years old in human terms, the same age as Kagome.”
Already we can see that RT herself did not have an answer for Inuyasha’s chronological age, because she didn’t consider it when she wrote the story, but she did make sure there would be no maturity age gap between him and Kagome. The other thing to note is that the 50 years he was pinned to the Sacred Tree does not count towards his aging, as he was magically sealed by Kikyo’s arrow (which makes sense, all his bodily functions must have stopped, otherwise he would have died of hunger or thirst after that long).
Following this, a book called InuYasha: Zusetsutaizan Ōgikaiden (Inuyasha Profiles) was released in 2003, in which Rumiko Takahashi is credited as the writer. It was published in English by Viz in 2007, and I have a copy of it at home. In this book, the ages of the main characters are revealed, and here’s what it says for Inuyasha:
For all non-human characters, their age says “_ (in human years)”. This is basically the same answer that Rumiko Takahashi gave in her first blog post: in human terms, Inuyasha is 15 years old, but chronologically he’s not (which we already know, because of the 50 years seal).
That being said, I want to start by addressing evidence that I’ve seen people have use from the manga to support the idea that Inuyasha is old and/or ages slowly. One moment that has been mentioned is this line in chapter 3:
Inuyasha basically brags that he wouldn’t be old after 50 years, unlike humans like Kaede. Some people argue this means he’s been alive for more than 50 years before being sealed, but remember that this is the same chapter where Inuyasha claims that Kikyo was his enemy and he is glad she is dead. He was putting on a tough guy act at this point, and we are not supposed to honestly believe what he’s saying. As far as we know, Inuyasha had not met other hanyo at that point in his life, and even if he did, he probably didn’t ask their age. So it’s completely possible he’s assuming or hopes he’s going to age slowly like full yokai do, since he doesn’t know yet and cannot compare himself to anyone. Because of that, this has never seemed like strong evidence to me.
There is though, one piece of evidence that completely blindsided me when I first read about it here, because I’m not really a Japanese history connoisseur and never noticed that detail, and it’s related to the clothing that Inuyasha and his mom wear. Essentially, Inuyasha is wearing a suikan, and Izayoi a juni-hitoe, which are both articles of clothing that were popular in the Heian era.
The Heian Era was from 794 to 1185 and the Inuyasha series takes place around the year 1550. Even if Inuyasha was 200 years old, that still doesn’t make him old enough to be from in the Heian period. He would have to be at least 365 years old, which is even harder to believe.
But I found a good reason to believe that Inuyasha and Izayoi’s clothing are not a good indication that they lived in the Heian period. In chapter 54 / episode 16, we see a flashback from 50 years earlier, of the moment when Naraku took different forms to trick Miroku’s grandfather and put the curse of the wind tunnel on him. Naraku/Muso did not live in the Heian period, and yet in his disguises he wears Heian clothing, including a suikan:
But most importantly, a juni-hitoe:
We can tell that it truly is a juni-hitoe because “she” is wearing red hakama pants under it, instead of a kosode:
So what is my conclusion? My best guess is that Rumiko thought “50+ years ago = old = period clothing”. There’s also the fact that the fire rat robe that Inuyasha wears is from The Tale of the Bamboo Cutter (a classic of Japanese literature), so Takahashi might have simply wanted to make Inuyasha’s mom look like Kaguya hime. Because of the conflicting evidence of Naraku wearing a juni-hitoe, I feel comfortable saying this was an artistic decision rather than a strong confirmation of the timeline in Inuyasha.
I’ll also add that RT admitted herself that she did not do much research for the purpose of writing/drawing Inuyasha in an interview in Animerica Vol. 9 No. 6 June 2001:
Q: To set the story in the Sengoku Era, did you gather material and research for this purpose? RT: It's not that I did that much research for the purpose of Inuyasha, I just used the knowledge that people would know even as a child, such as the image of samurai wearing armor and riding horses- from that type of perspective. Also, for example, say castles from a certain time took a popular type of form. There are many different forms of castles, but after a certain period of time passes, castles become more grandiose and I can say that Inuyasha is set before that time.
The last piece of “word of god” confirmation I want to address regarding Inuyasha’s aging, is something that unexpectedly came years later when Hanyo no Yashahime, the anime-only sequel to Inuyasha, was released. In this series, Inuyasha and Kagome have a child: Moroha. Moroha is very special, as she was born to a half-demon and a human, something we’ve never seen before. The question of her aging was also raised amongst fans, and so RT was asked the question in Shounen Sunday S for their December 2020 issue.
Q: “In Yashahime, Inuyasha and Kagome’s daughter, Moroha-chan, appears. Inuyasha is half-demon, Kagome is human, and Moroha-chan is a half-demon and human mix. Do the three of them age differently in the Warring States Period? ” RT: “They seem to age at about the same pace as the timeframe of the story. Signs of their aging may show up decades later.”
- Translation also by lilyginnyblackv2 from this post.
When she says “age at the same pace at the story” I understand that when one year passes chronologically in the story, Inuyasha, Kagome and Moroha age by one year. This implies normal human aging. Same with her comment about “their aging may show up decade later”. As we’ve seen in Yashahime, human characters in their forties and even sixties barely had wrinkles and grey hair, so yes, it does take decades for anime characters to show any signs of aging. I mean Mama higurashi gained (1) streak of grey hair in 20 years:
This 2020 interview should have been the final nail in the coffin that buries the “Inuyasha is old and ages slowly” discourse, in my opinion, but it apparently wasn’t enough for everyone. So we will continue and dig even deeper into manga evidence and the logistics of hanyo biology.
Oh and one more thing regarding word of god from Rumiko Takahashi: in the “Trivia” section on Kagome’s page on the website Heroes Wiki, it used to say: “Rumiko confirmed that Kagome doesn’t age in the feudal era” without providing any source or evidence of her saying that. A screenshot of this wiki made the rounds in 2020 and unfortunately led a lot of people to believe this misinformation. If people don’t believe me when I say there is no proof of RT ever saying that, then I hope at least that Takahashi’s statement in Shounen Sunday S makes it clear that Kagome age “at about the same pace as the timeframe of the story” and she is not frozen in time because she’s from the future. Actually, I think this idea came from the second movie (once again, not written by RT), where it implied that Kagome was not affected by time magic. But this is not a post about Kagome so I won’t delve into it further.
2. Yokai aging
Before we dive into the topic of yokai aging, let’s first make sure we’re on the same page about what a yokai even is in the context of Inuyasha. Yōkai (妖怪) are a category of supernatural beings in Japanese folklore, which includes monsters, spirits, and demons (but it’s always translated as “demon” in official English translations). In the Inuyasha series, we see that some yokai that are created through magical or spiritual means, while others are born through sexual reproduction. For example, Yura is essentially a possessed hair comb, which explains why her human-like form is youthful and most likely won’t change over time. But when we talk about yokai aging, what we're really interested in are yokai born to yokai parents. These are usually inspired by mammals, like the dog demon brothers (Inuyasha and Sesshomaru), kitsune / fox demons like Shippo, or wolf demons like Koga.
One common misconception in this fandom is that these animals-yokai like Sesshomaru are immortal, when they are pretty explicitly proven to NOT be. First off, Rumiko Takahashi addressed this in the same 2001 blog post on websunday.net where se talked about Inuyasha’s age:
“One of the most common questions I receive in fan mail is, "How old are Inuyasha and the others?” [...] As for youkai like Shippou, Sesshoumaru, and Kouga, they can live for dozens or hundreds of years, so I think it would be best for the readers to make their own judgements based on appearances.”
- Translation by inu-fanon from this post.
We have a confirmation that these yokai have long lifespans, but they will not live forever. One direct example of this, is the yokai Hosenki. Inuyasha meets is son Hosenki II in chapter 298, who is himself a yokai who is hundreds of years old (since we learn that waiting 100 years is nothing to him). But what’s most important to note is that he explicitly says his father died of old age:
The Hosenki family are probably oyster yokai (they cultivate magical jewels), so not mammals, but a molluscs that reproduces sexually (yes we’re still about Inuyasha here, bear with me).
We can then take a look at the other yokais that have explicit ages in the manga to get an idea of what Rumiko Takahashi considers “old”:
In chapter 394, a cat yokai is old enough to be considered mature at 300 years old:
And Bokuseno is pretty much considered ancient at 2000 years old (chapter 183):
Sesshomaru himself is at least 65, since he’s older than Inuyasha and has interacted with him before he was sealed, but that’s all we know.
And finally there’s the badger yokai Mujina in chapter 384 who says her dad has been dead for hundreds of years:
As we can see, being hundreds of years old is worthy of mention for yokai, which would make it weird for someone who is only half demon to be as old as them and for it to not be mentioned.
So it’s time we compare Inuyasha to people who are like him, other hanyo, and talk a bit about the half demon aging logic / conversion that a lot of people seem to think is canon. The most popular theory I’ve seen is that “10 years in the timeframe of the story = 1 year for a hanyo”. This also comes from the idea that Inuyasha is 200 years old, because minus the 50 years spent sealed, Inuyasha would have spent 150 years alive and awake, and he is mentally 15 years old, so 15 * 10 = 150.
This sounds like a nice and easy conversion, but I want to point out that even Sunrise doesn’t seem to believe that hanyo age at a “10 years for 1 yokai year” rate, at least not during a hanyo’s early years.
There is a flashback of Inuyasha as a child with his mother in episode 6 of the anime, where Inuyasha looks to be 5-6 years old. According to the theory, 50-60 years should have passed and Izayoi should be an old woman... But she’s not.
Now in the sequel “Hanyo no Yashahime”, we know that Towa and Setsuna, who are both inu hanyo of the same bloodline as Inuyasha, are 14 years old mentally, physically, and 14 years have passed in the story. They are not 140 years old.
So the second theory that I’ve seen, is that hanyo might have “logarithmic aging” or the Immortality Begins at 20 trope, where they age like a human up until puberty or so, at which point the aging process slows down or stops. The idea is that they reach their “prime” and then their supernatural abilities protect them from the degenerative effects of aging (wrinkles, muscle atrophy, etc).
So to address this point it’s time we look at the other hanyo we meet in the manga. The other hanyo we see are also born from a yokai parent that is mammal-like but has a humanoid form. As a note, Sango says in chapter 86 that powerful yokai (daiyokai) often have a human-like appearance, and since Inuyasha’s father is a dog yokai with a humanoid form (only seen in the 3rd anime movie but confirmed to be designed by Takahashi), I think these hanyo are of comparable strength to Inuyasha and thus it’s fair to compare their aging process. Also as with yokai, some hanyo like Naraku are born not of reproduction, but other means, like demonic fusion. We won’t address hanyo like him since there is nothing to analyze, really.
Shiori: She is a hanyo whose father is a bat yokai (chapter 214):
Shiori looks young, I would say 8 or 9 years old. We already know that the previous age conversion rate does not work, since she would have been alive for almost 100 years now but her human mother is still very much alive and a young woman:
So unfortunately Shiori does not give us a lot more information. But there is another hanyo who is more interesting…
Jinenji: He is often believed to be a horse yokai due to his long nose, but there’s no evidence of that. We just know that his father had this humanoid form:
What’s interesting is that it’s harder to tell Jinenji’s age. He is introduced in chapter 112, which is called “The Earth Boy” in English translations, and “boy” is usually a term for a young male, but from what I found “Earth Boy” is the translation of his name. The Japanese title for the chapter is simply: 地念児, "Jinenji" (source). Anyway, there are some things to note about his appearance:
Kagome notices that he has some old scars, and we can also see that he has a balding head / receding hairline. His father didn’t have a balding head, he had very long hair at least in his humanoid form. To me, if he was more human-like Jinenji would look like a middle-aged man. His mom mentions that she met his dad when she was “around Kagome’s age” (chapter 113), so let’s say she had him when she was 18, and Jinenji is let’s say 50 years old chronologically, she would be 68....
Considering the fact that she works outside in the fields all day, I think she does look like a human woman in her 60s. Kaede is also supposed to be in her 60s, and has the same sort of wrinkles.
As I mentioned, the general argument is that, due to Inuyasha’s regenerative ability (which allows him to heal quickly and regrow his fang in half a day) he would age much more slowly compared to a human. My counterpoint here is that Jinenji also has enhanced durability like Inuyasha does (since he could endure the flesh eating saliva of the insect demon) but despite that he does have old scars and signs of aging as a hanyo. My theory is that these abilities get weaker with time or they don’t slow down aging.
At this point, we’ve mostly entered the real of theories, but I will share a little bit of what I believe is going on biology-wise regarding hanyo.
3. Biology
We don’t have clear canon lore on yokai biology, and yokai are fantastical creatures anyway so I don’t think we should think too deeply about their number of chromosomes and how it’s possible for them to reproduce with humans (this is Rumiko “I don’t think about this and neither should you” Takahashi after all). But what we do know, as explained by Myoga in chapter 40, is that all hanyo have a “period of weakness” where they lose their demon powers and turn human:
To me, the way he explains it implies that a hanyo’s “base biology” is mostly human, but they have yoki (demonic energy) in their blood that gives them powers and otherworldly features. Since Inuyasha was born from a human mother in a human womb, and aged at the same pace as humans at the beginning of his life, to me this all point to the fact that on a biological or cellular level, Inuyasha is more human and what he inherited from his father is mainly his demonic energy. We can also note that the features he inherited from his father, like his white hair, yellow eyes, dog ears, fangs and claws completely disappear when he doesn’t have his demonic power.
What also makes me believe that a hanyo’s biology is fundamentally different from a full yokai, is Inuyasha’s “full yokai” form. Even when he’s in that form, he’s still not like his full yokai father and half-brother. He can’t transform into a gigantic dog, his body stays the same but he “loses his mind” because the demonic energy in his blood becomes too strong. The manga describes it as “unleashing/awakening his yokai blood” in chapter 157.
Lastly, I found this cool post from @inu-fiction that also argues that Inuyasha is more human than demon because he got all his mitochondrial DNA from his human mother. I only took one biology class in university so I definitely do not have enough biology knowledge to add to this topic, but I wanted to mention it as well since it’s supports my argument.
4. Mental development & narrative
My last issue with the idea that Inuyasha is already hundreds of years old at the beginning of the series, relates to Inuyasha’s mental age, or his maturity level. As we saw in Rumiko Takahashi’s websunday blog post, she wants us to see Inuyasha as a 15 year old boy, who is equal to Kagome. If we believe that he has been alive and awake for 150 years, and he grew up like a human until the age of 15, this means that he hasn’t matured at all in 135 years...? If Inuyasha has already been through puberty and is technically an adult, shouldn’t his mental age reflect his life experience now? How long is it going to take before we can consider him 16 “in human years”?
The story in the manga/anime took less than a year, and we saw how much Inuyasha matured and learned over the course of the series.
When we meet him, he doesn’t seem to have more knowledge of the world than his human friends. When you start thinking of all the things Inuyasha experienced for the first time during the series, it doesn’t make much sense for him to be older than he looks. Myoga is his vassal, and even he didn’t even know that Inuyasha’s human moment is during the night of the new moon!
You could argue this is simply for the sake of the plot and so we the audience, experience his growth journey (obviously), but that doesn't explain why he seemingly didn't gain any knowledge from 100+ years of life experience.
Also, much of his story centers on the fact that he grew up alone, but he has finally found a place to belong with Kagome and his friends. If Rumiko Takahashi had intended for him to be significantly older than them, and for him to be someone who would outlive them by centuries, I believe she would have mentioned it explicitly at some point. Overlooking this would be a major issue, since his friends and wife are human, meaning he would be alone again relatively soon if that were true. This becomes even more obvious when you consider that Takahashi has other series where the protagonist’s old age is explicitly stated in the manga: Yuta from Mermaid Saga is stated to be over 500 years old, and Mao from the series of the same name, is over 900 years old. I’m not caught up on Mao, but in Mermaid Saga (a series that she released before Inuyasha) the topic of immortality and long lifespan is directly addressed and is a major issue for the character concerned. So why not do the same in Inuyasha, if he also has a long lifespan? Because it’s simply not an issue we should worry about, in my opinion.
6. Conclusion
tl;dr: The theory that Inuyasha and other hanyo have “logarithmic aging” is not impossible, but considering the facts that this was never brought up in the original series, doesn’t seem to be the case for Jinenji, and Inuyasha’s character and experience does not reflect someone who has been alive for centuries, I personally believe it makes more sense for hanyo to have a aging process that is closer to humans. Rumiko Takahashi's answer in a 2020 interview where she states that Inuyasha age "at the same pace as the timeframe of the story" also seem to indicate that she reached that conclusion after finishing the story, once she had to consider the reality of him outliving his family if he did age like a yokai. Therefore, Sunrise making Inuyasha 200 years old in the third movie doesn’t appear to fit coherently with what Rumiko Takahashi envisioned for his character and will never be canon to me.
