A series with as characters as Demon Slayer: Kimetsu no Yaiba has of course produced a few that became unexpectedly popular.
- Sabito and to a lesser extent, Makomo for their role in helping out Tanjiro and the reveal that they were both Dead All Along made them seen as Too Cool to Live and tragic in the eyes of the fandom. Sabito is especially so to the fandom due to his connection and relationship with Giyu back when he was still alive.
- Susamaru, the Temari Demon has a small but loyal following. Due to her Blood Knight personality, attractive design and sad sendoff she's become the star of many a fanwork to give her more screentime.
- Mukago is significantly more popular than other Lower Ranks (excluding major antagonists Rui and Enmu) for being the only female, and a rather cute one at that.
- Rui himself is the first major antagonist, but still fairly small in the scale of the series. This is due to being in what's regarded as one of the best fights of the entire series (and when many people agree the series started Growing the Beard), his eerily calm personality, and his tragic backstory.
- For a character that wasn't even the main antagonist of the arc where she appeared, the Spider Demon Mother gained some popularity thanks to her attractive design, tragic backstory, and beautiful death scene, becoming the most loved member of Rui's fake family after Rui himself.
- Kyojuro Rengoku is an extremely popular Hashira and one of the most popular characters in the entire series due to being an enthusiastic Nice Guy, his awesome fighting skills, and his tragic death at the hands of Akaza. His popularity has gotten to the point where many are surprised to learn that he only has a major appearance in one arc.
- Doma is one of the most popular (if not the most popular) demons in the series, despite only having a truly major appearance in the final arc, due to being an extreme yet interesting example of The Sociopath, his creepily outgoing personality, having several comedic moments, and his connection to Shinobu and Inosuke. His looks certainly didn't deter fans away either. Some have even gone so far as to say that they wish he was the series' main villain instead of Muzan.
- Oddly enough, Kaigaku gets this from some fans despite being a pure Hate Sink, mostly attributed to being an interesting character with wasted potential.
- Despite not having as extensive a role as Giyu or Shinobu, Muichiro Tokito is one of the Japanese's favorite Hashira, reaching third place in the second popularity poll and surpassing Nezuko herself.
- While Hantengu is usually regarded as nothing more than an ugly and cowardly Hate Sink, his emotion clones (minus Urami who is often disregarded or disliked due to his limited screentime and resemblance to him): Sekido, Aizetsu, Karaku, Urogi, and their combined form Zohakuten got their own fanbases thanks to their designs, abilities, and distinct personalities, especially when they were animated and voiced come the Swordsmith Village arc's anime adaptation. Aizetsu stands out in particular, due to being the Token Good Teammate, and fans finding his timid and somber demeanor endearing. Zohakuten is also a fan favorite due to his sheer power, and awesome appearance.
- Gyutaro is a character whose existence isn't revealed until midway through the Upper-6 fight, which ends with his death, but many fans like him for an excellent fight, his tragic relationship with his sister and his status as an Evil Counterpart to Tanjiro.
- Mitsuri's parents, Mr. and Mrs. Kanroji. Due to their expanded role in the anime and distinction as being Good Parents who are still alive no doubt, they have become immensely popular and likable characters.
- The female Kakushi who accompanied Tanjiro to the Swordsmith Village arc. She's gained some fans for her precocious crush on Tanjiro and curvy figure.
