WARNING: The following contains spoilers for Demon Slayer: Kimetsu no Yaiba #204, by Koyoharu Gotouge, John Werry and John Hunt, available now in English from Viz Media.
Demon Slayer: Kimetsu no Yaiba became one of the most popular manga/anime series of the past few years and follows Tanjiro and Nezuko's journey to finding a way to change demons back to humans. However, with all the interesting characters met along the way, there is plenty of potential for untold stories.
Hashira of the Past
With death always looming, the life of a Demon Slayer is difficult and often short. Those who survive their time are sure to have a myriad of interestingly terrifying stories, especially if they're a Hashira. Curiosity can't help but cause fans to wonder what Giyu and Tanjiro's master Sakonji Urokodaki, the former Water Hashira, or Jigoro Kuwajima, the retired Roaring Hashira that trained Zenitsu, accomplished during their time with the Demon Slayer Corps. A whole separate series could chronicle the history of the Rengoku family's lineage of Flame Hashira.
Though the stories of past Hashira would undoubtedly have plenty of demon-slaying action, as we've already seen with the likes of Urokodaki, sorrow and pain remain destined to be a part of that tale as well. After all, the series revolves around themes of loss and how various characters handle it. Nonetheless, seeing how these swordsmen rose through the ranks to become Hashira is something fans would be happy to sink their teeth into.
Hashira of the Present
The current generation of Hashira plays an integral part in how the series unfolds. While we see them in action and get some glimpses into their pasts, seeing more of any of these characters would be a welcomed addition to the story. Giyu Tomioka, the Water Hashira, and Kyojuro Rengoku, the Flame Hashira, are the two with arguably the most meaningful relationships with Tanjiro. Seeing a couple of one-shot stories about the sullen Giyu, struggling with his survivor's guilt, or the eccentric Rengoku's unwavering sense of honor explored further should excite any fan.
Though we know how the lives of most of the Demon Slayers ended up as the series comes to a close, there are still some unexplored stories. An alternative version of the story that sees Sanemi Shinazugawa, the Wind Hashira, and his younger brother Genya working together, instead of at odds, would be an unstoppable force of brotherly love. For those wishing to mend their broken hearts after the tragic deaths of Mitsuri Kanroji, the Love Hashira, and Obanai Iguro, the Snake Hashira, how about a chance to see the relationship that never was? With Marvel's What If...? series popular among comic book fans, it wouldn't be breaking new ground to give manga lovers some stories that "could have been."
Yoriichi Tsugikuni
Most of Yoriichi's story is told second-hand through his brother Michikatsu - later known as Kokushibo as a demon - and through Tanjiro's inherited memories from his ancestor Sumiyoshi and Muzan. This leaves most of Yoriichi's story untold, making him a character worth exploring further. Known as the most powerful Demon Slayer in history and creator of Sun Breathing, there would be plenty to uncover about the mysterious swordsman.
After failing to kill Muzan and the revelation that his brother had become a demon, Yoriichi was banished from demon-slaying. Did he go into a Yoda-like exile, or did he continue hunting Muzan? Exploring this blank period from the strongest character in the series could be a real page-turner.
Nezuko
Though Nezuko is present for much of the story, it isn't necessarily clear what she goes through while she is a demon. Fans can only speculate Nezuko's internal struggle, given the flashes we see within her subconscious and the constant conflict with the demonic desires forced upon her. Another idea for a "What if...?" story would be if Nezuko and Tanjiro reversed fates, which is even depicted in the title page of the serie's 100th chapter.
One of the beautiful things about Demon Slayer is its cast of fascinating characters. Whether we'll see any additional stories from the series is unknown, but with the Kimetsu no Yaiba movie still to be released, there is still plenty for fans to be excited about!