Tanjiro, Zenitsu, and Inosuke are undoubtedly the three characters that make up the core trio of Demon Slayer. With Tanjiro's unwavering determination, Zenitsu's hidden potential, and Inosuke's promising abilities, the three of them make a formidable team of demon slayers. Despite their importance to the story, it's surprising to many fans that Zenitsu and Inosuke are absent from the Swordsmith village arc. While some may worry about the separation of the trio, it's worth considering whether there is a narrative reason for their absence. Perhaps their exclusion was to allow for the development of other characters and a deeper understanding of those we haven't seen since season 1.
The Coincidental Reasons
After battling Upper Moon 6 Gyutaro and Daki, Tanjiro, Zenitsu, and Inosuke suffered severe injuries, requiring individual recovery time. Tanjiro was the last to awaken from his coma and, unfortunately, Zenitsu was already on a separate mission by the time he did. Inosuke, on the other hand, woke up around the same time and immediately went on a separate demon slaying mission during a montage. The members' duties are assigned on a singular basis, which is why Zenitsu and Inosuke were sent out promptly. Meanwhile, Tanjiro focused on Rehabilitation Training to heal from the injuries sustained during the Entertainment District Arc, delaying his return to missions. Interestingly, Tanjiro found himself in the Swordsmith Village because he needed a new sword after breaking his previous one. Although Haganezuka initially refused to make him one, Tanjiro's goal was solely to convince him to smith a better blade for future demon slaying endeavors.
The Narrative Reasons
From a narrative perspective, the decision to split up Tanjiro, Inosuke, and Zenitsu was an interesting one by the author, as it allowed for character development and sharing the spotlight with new characters like Muichiro and Mitsuri, both Hashira's of the Demon Slayer Corps. This provided the audience with an opportunity to learn more about these characters and also gave a temporary break to Inosuke and Zenitsu's development, allowing other characters to endear themselves to the audience. While some may complain about removing certain characters for an entire arc, this decision ultimately benefits the series by allowing for a focus on the other characters that Demon Slayer has to offer for future arcs.
The introduction of new characters, such as Mist Hashira Muichiro and Love Hashira Mitsuri, offers a fresh perspective into the opinions of Tanjiro and Nezuko among the Hashira. In addition, the development of Genya's character arc is highly anticipated, given his recent revelation as being related to one of the Hashira. With the looming threat of Upper Moons 5 and 4, the success of the upcoming arc may require the assistance of not only skilled Demon Slayers, but also Hashira like Muichiro and Mitsuri. Ultimately, the decision to remove Zenitsu and Inosuke from the arc serves to expand the character cast and shift the dynamics and powers, ensuring the importance and development of all characters involved.