Demon Slayer: Kimetsu No Yaiba has exploded in popularity and has become one of this year’s best anime. Based on the manga by Koyoharu Gotōge, its characters are wonderfully layered and diverse in their motives and personalities, its plot is engaging and emotional, and its animation, by studio Ufotable, is beautiful and, at times, absolutely breathtaking.
Kimetsu No Yaiba also excels in its nuanced subtleties and clever foreshadowing. It’s easy to miss some of the hidden details upon first viewing, so here are ten cool details that viewers may have missed throughout the first season.
10 Tanjiro's Hanafuda Earrings
Tanjiro wears a pair of hanafuda earrings that he inherited from his father. When Muzan Kibutsuji, the series' villain who turned Nezuko, Tanjiro’s sister, into a demon, sees Tanjiro’s earrings, he sends two of his subordinates after the young Demon Slayer. Muzan had a past encounter with a Demon Slayer who wore similar earrings.
This past slayer also had red hair, similar to Tanjiro. Later, when Tanjiro is fighting the Lower Moon Five of the Twelve Kizuki, he recalls when his father said that he wanted his kagura technique and the hanafuda earrings to pass to Tanjiro uninterrupted, further emphasizing the mysterious importance of the hanafuda earrings.
9 Mr. Urokodaki's Sense of Smell is as Keen as Tanjiro's
One of Tanjiro’s defining traits, aside from his kindness and empathy, is his keen sense of smell. He can even pick up on the intentions of others, and, once he gets stronger, can use his sense of smell to determine how many humans a demon has consumed.
However, Tanjiro isn’t the only person to have such a keen sense of smell. His teacher, Mr. Sakonji Urokodaki, also possesses this ability. When Urokodaki first meets Tanjiro and Nezuko in their battle against the temple demon, he states that Tanjiro has the “scent of kindness” and determines that the boy is too kind and can’t make decisions when it matters.
8 Tanjiro's Warding Mask Is Unique To Him
Once Sakonji Urokodaki’s students complete their training, he carves them a fox-themed warding mask to wear during their Final Selection. These masks are charged with a protection spell.
Each mask has a different design that is unique to the wearer. Sabito’s mask had a pale scar in the same spot as the scar on his cheek, while Makomo’s mask had flowers that reflected the flowers on her kimono. Tanjiro’s mask has a red, sun-shaped symbol over his scar. The color and shape of this symbol resemble the design on Tanjiro’s hanafuda earrings, too.
7 Tanjiro's Scar Changes
Tanjiro’s head scar is an unmistakable part of his design that has been present since the first episode. While manga readers know how Tanjiro got his scar, anime watchers will have to wait for that backstory. However, Tanjiro’s scar does change in the first season.
During Final Selection, Tanjiro is attacked by the Hand Demon, a demon responsible for the deaths of Mr. Urokodaki’s past students, including Sabito and Makomo. During the fight, the Hand Demon strikes Tanjiro, smashing the warding mask covering Tanjiro’s scar. When Tanjiro’s wound eventually heals, his head scar has a new color and shape.
6 Only Demons With Unlimited Potential Can Become One Of The Twelve Kizuki
Kimetsu No Yaiba’s main antagonist, Muzan Kibutsuji creates demons using his blood. If a demon happens to show potential, Muzan will share more of his blood with that demon, blessing it with even more power. The twelve strongest of these demons make up the Twelve Kizuki. However, if a Kizuki reaches its limit, they become useless to Muzan and have their title and number stripped. The demon Kyogai is a prime example.
When he is first introduced, Kyogai is after humans known as marechi (their blood is worth about fifty normal humans for a demon), because he wants to regain his position as one of the Twelve Kizuki. He was originally the Lower Moon Six, but reached his limit and had his title and number taken by Muzan.
5 Tanjiro is Incredibly Clever
Tanjiro isn’t just empathetic and kind to everyone he meets; he’s also incredibly clever. This is evident even before he becomes a member of the Demon Slayers. In his fight to protect Nezuko from Giyu, Tanjiro is clearly outmatched. However, despite his fear and the overwhelming situation before him, he quickly comes up with a plan that almost works and manages to impress Giyu.
After Tanjiro trains with Urokodaki, passes his Final Selection, and becomes a Demon Slayer, his cleverness continues to evolve along with his skills. This quick-thinking and ability to plan not only impresses Tanjiro’s peers, but has helped Tanjiro survive numerous battles and defeat multiple demons.
4 Don't Call Muzan Pale Or Dead
Muzan is the ideal antagonist. He’s strong, dangerous, and will eliminate anyone who gets in his way. He has created most of the man-eating demons in Kimetsu No Yaiba , and he even states that he’s “a living being who’s infinitely close to perfection”.
However, Muzan can’t tolerate being called pale or dead. After his initial encounter with Tanjiro, Muzan is preparing to send his underlings after the Demon Slayer when he bumps into three drunk humans. Muzan is content to leave them alone, and he even apologizes, despite the group’s rudeness. Then, one of the drunks comments on Muzan’s pale skin and how he looks ready to fall over, dead. Suddenly, Muzan’s demeanor changes. His eyes flash in irritation and anger, and he kills the group without remorse or hesitation.
3 Nezuko is Unusual, Even Among Demons
Nezuko is as adorable as she is unique. Multiple times throughout the season, characters have commented on how Nezuko is different from other demons. For one, she doesn’t require human blood to survive; instead, she restores her strength through sleeping. She also displays incredible power and adaptability in her fights.
Other demons, including Tamayo, Yashiro, and the Lower Moon Five, have commented on Nezuko’s unique aura and abilities. Tanjiro asks Mr. Urokodaki if her uniqueness could be a Blood Demon Art, but Mr. Urokodaki doesn’t believe so. Now that Nezuko has learned her Exploding Blood Demon Art, it’s expected that her unique powers and cuteness will only continue to grow.
2 Giyu and Sabito Have Similar Outfit Patterns
Outfits and the patterns on them are very significant. Clothing makes important characters stand out, so that it's easier for viewers to distinguish them from background characters (consider how the protagonists in Kimetsu No Yaiba all have unique garments over their Demon Slayer Uniforms). Sabito and Giyu having similar patterned clothing is unique.
The only other characters with similar pattern themes are Shinobu Kocho and Kanao Tsuyuri, because Kanao is training under Shinobu. When Giyu first meets Tanjiro, the frame focuses on this unique clothing pattern when Giyu mentions that he understands the despair and loss that Tanjiro is feeling, which, given Sabito’s fate, could hint at a connection between the two. Manga readers will already know the answer to this mystery, but anime viewers will have to wait and see.
1 Kamado Family's Connection to Fire
The Kamado family works with fire, but Tanjiro and Nezuko's connection to the element has grown throughout the first season. When the swordsmith, Haganezuka, delivers Tanjiro’s sword, he calls Tanjiro a “Child of Brightness” because of his red hair and red eyes. It’s considered lucky in families that work with fire. Later, when Tanjiro fights against the Lower Moon Five demon, he has a flashback of his father, who shares Tanjiro’s eye color, scar, and hair color.
When Tanjiro remembers his father’s fire-based kagura dance, he realizes that his father taught him a powerful breathing technique. When Tanjiro uses this, he unleashes the Hinokami Kagura Dance, a powerful move that turns his water into fire. Similarly, Nezuko’s Demon Blood Art is fire-themed. Her Exploding Blood takes the form of pink flames when she uses it.