Well, in 'kimetsu no yaiba the first novel', it probably focuses on the early days of the main characters. It could be about Tanjiro's journey as he first discovers the existence of demons and decides to become a demon slayer. It might also include his encounters with other important characters like Nezuko, and how their relationship develops in this different narrative format.
Kimetsu no Yaiba manga is highly popular. It has captured the hearts of many readers with its engaging storyline and well-developed characters. The beautiful art style also adds to its appeal.
Nezuko Kamado, Tanjiro's sister, is also a main character. Despite being a demon, she retains some of her humanity and is very protective of her brother.