Throughout the Demon Slayer series, fans are treated to a variety of post-credit scenes at the end of selected episodes, which provide additional pieces of information about the story or one of the characters. These tidbits are referred to as "Taisho-era secrets."
Some of these secrets hold little to no real significance and serve no real purpose other than to be comically entertaining or to provide a look into the minutiae of specific characters, while others impart a slice of knowledge that every Demon Slayer fan can appreciate knowing.
10 Zenitsu Becomes Self-Conscious In Front Of Girls
One of the most surprising Taisho-era secrets in Demon Slayer is the revelation that Zenitsu becomes self-conscious in front of girls. The reason for this is that Zenitsu's behavior often seems to indicate the contrary. Granted, while it is possible that Zenitsu behaves the way he does to mask the fact that he feels self-conscious, it neither justifies nor explains his lack of decorum.
Throughout Demon Slayer, Zenitsu's indecorous behavior is most apparent when he is around women. In fact, when Zenitsu is reintroduced to the audience following Final Selection, it is while harassing a girl and imploring her to marry him. Zenitsu's conduct is strangely odd for someone supposedly self-conscious around the opposite sex.
9 Inosuke's Kasugai Crow Stays Invisible
After completing the Final Selection, the survivors are each assigned a Kusugai crow. Conspicuously absent, however, is Inosuke's crow, which doesn't make a single appearance in the series. Thankfully, Tanjiro reveals exactly why Inosuke is the only one not seen at any time with his own crow.
It turns out that Inosuke's crow is always by his side, but due to the boar-hide-wearing Demon Slayer trying to eat it, it stays invisible. Considering the type of person Insouke is, this revelation isn't entirely surprising, but it does help to further cement just how eccentric Inosuke really is.
8 Medicated Water Is Used To Heal Wounds
Tanjiro reveals that the medicated water he, Zenitsu, and Inosuke use for reflex training is added to their baths as it is beneficial in helping to remove exhaustion and heal wounds. Given how rigorous the training regiment is in Shinobu's Butterfly Mansion combined with the Demon Slayers' experiences on Mount Natagumo, it makes sense that they would need to employ various methods to aid with healing.
Since Tanjiro, more so than anyone else, is heavily involved in undertaking this difficult training while at the Butterfly Mansion, it is most appropriate that he reveals this information, which helps to further establish how important the healing process is to Shinobu and her assistants.
7 Zenitsu Enters Final Selection Due To Being Slapped By His Master
Tanjiro reveals that Zenitsu was brought to Final Selection after being slapped by his master for refusing to take the selection exam. At this point, fans know little about Zenitsu as he hasn't been seen much other than very briefly at Final Selection.
This revelation foreshadows what to expect from Zenitsu going forward, giving a small insight into his character and the type of person he is. It also shows the disparity between Tanjiro, someone determined to become the best Demon Slayer possible, and Zenitsu, someone only involved with the Demon Slayer Corps due to some unfortunate circumstances.
6 Urokodaki Wears A Mask Because His Face His Too Kind
Sakonji Urokodaki's face is never shown in Demon Slayer despite his significant appearances in the series. It seems strange that Urokodaki would don the mask at all times until Tanjro reveals the reason behind his master's decision. Tanjiro confirms that demons had, in the past, made fun of Urokodaki for having such a kind face.
Given that Urokodaki is a formidable Demon Slayer, it isn't surprising that he would want to prevent his adversary from assuming his appearance to be a weakness. That being said, he could also use it to deceive his demon opponent into letting their guard down. In any event, Tanjiro's revelation provides an intriguing, albeit small, insight into Urokodaki's backstory.
5 Kagaya Ubuyashiki Is The 97th Leader Of The Demon Slayer Corps
Learning that Kagaya Ubuyashiki is the 97th leader of the Demon Slayer Corps highlights just how long the Demon Slayers have been operating in the world of Demon Slayer. Rengoku stating how important it is that he and the other Hashira members do not squander their opportunity under Ubuyashiki also shows the respect they have for him.
Interestingly enough, this secret, revealed by Rengoku, very subtly adds to Rengoku's character arc. It is this respect and admiration for Ubuyashiki and the Demon Slayer Corps that sees Rengoku valiantly fight against the Upper Rank Three Demon, Akaza.
4 Rengoku Has No Tsuguko Training Under Him
It is revealed during Demon Slayer's first season that Kanao is the Tsuguko of Shinobu, an apprentice or eventual successor to a member of the Hashira. Tanjiro reveals that Rengoku does not have a Tsuguko due to the difficult nature of his training.
Tanjiro mentions that everyone who has previously trained with the Rengoku has run away, but declares his willingness to train with a Hashira if it means being able to turn Nezuko back into a human. He proceeds to ask Rengoku to train him, but, unfortunately for the young Demon Slayer, Rengoku is fast asleep on the Mugen Train.
3 Nezuko Reveals Her Mother Once Head-Butted A Boar
To say that Tanjiro's head-butts are devastating would be a tremendous understatement. Although they aren't necessarily effective against the more dangerous demons, Tanjiro has certainly used his head to great effect against the likes of Inosuke and the Wind Hashira, Sanemi Shinazugawa.
It is for this reason that it is interesting to learn from Nezuko that Tanjiro gets his rock-hard head from their mother, who once used a head-butt of her own to scare a boar away. Another interesting thing to note is that this is the only Taisho-era secret in the series to be revealed by Nezuko.
2 Shinobu Formulates Her Poison Inside Of Her Scabbard
Among the more fascinating Taisho-era secrets is Shinobu's revelation that the poison she possesses during battle is actually formulated inside of her scabbard. Taking into account the fact that Shinobu's lack of strength means she is unable to cut off a demon's head, it is completely reasonable that this information would be kept a secret.
Shinobu confirms that it is only her and her swordsmith who are aware of exactly how the poison is prepared. Shinobu more than makes up for what she lacks in strength with the potency of her incredible poison, which is used to devastating effect on the Spider Demon daughter on Mount Natagumo.
1 Susumaru And Yahaba First Meet On The Night They Attack Tamayo's House
The most surprising Taisho-era secret in Demon Slayer is by far the revelation that Susumaru and Yahaba first meet on the night they attack Tamayo's house. What makes this revelation so astonishing is that the two work in tandem as though they have done so many times before.
Tanjiro himself acknowledges how incredible it is that the two demons are able to coordinate so well when he highlights just how in sync the two are. This secret helps to accentuate the strength and formidable nature of the Demon Slayer Corps' foes and further underscores why Tanjiro, Nezuko, Tamayo, and Yushiro had such difficulty overcoming Susumaru and Yahaba.