Demon Slayer is known for its tragic moments and characters. In the story, demons roam the land slaughtering families and spreading misery wherever they go. However, despite the grief and sadness in the series, the bond between Sakonji and his students brings a sense of familial affection to Demon Slayer. Their relationship is much more than master and pupils. Each of the Water Breathing users sees the other as a type of family that they wish to protect, even at the cost of their own lives. In a world of tragedy, the Water Breathing users are a tight-knit and powerful found family.
Sakonji Urokodaki
Sakonji was the former Water Hashira for the Demon Slayer Corps and taught many individuals the art of Water Breathing. Although Sakonji appears stern and a ruthless trainer, he cares deeply for each of his students. He views all of them as his own children and worries about their safety. When Tanjiro returns after completing Final Selection, a test that led to the deaths of thirteen of Sakonji's other students, he openly weeps, glade that Tanjiro is alive and proud that he succeeded. Sakonji fully believes in Tanjiro's goal of restoring his sister's humanity and is willing to do whatever it takes to help him accomplish that goal. Sakonji is a father figure to his students, and like any good father, he wants the best for him.
Giyu Tomioka
Although Giyu maintains a stoic and cold persona most of the time, he still behaves like a protective older brother to Tanjiro. As a member of the Demon Slayer Corps and the current Water Hashira, it was Giyu's responsibility to kill Nezuko once she became a demon. Instead, he chose to inspire Tanjiro to fight for his sister and lead him down the path of becoming a Demon Slayer. Even after years apart, Giyu was willing to break the rules again and fight another Hashira in order to protect Tanjiro and Nezuko. Giyu's belief in Tanjiro and his goal goes so far that he was willing to kill himself as repentance if Nezuko were to ever kill a human.
Sabito and Makomo
Sabito and Makomo were two of Sakonji's students who died during Final Selection. Because they were unable to return to Sakonji, their father figure, their souls could not rest in peace. When Tanjiro begins his training, Sabito and Makomo assist him greatly. Sabito trains his body through their duels while Makomo improves his form and technique. The two students are heavily invested in Tanjiro's training because they want to see him succeed where they failed, and wish to ease Sakonji's grief over their deaths. They are two children who want their little brother to do well and for their father to be happy again.
Tanjiro Kamado
Tanjiro fills the role of the younger brother in this found family. He is excited to learn all he can from Sakonji, Giyu, Sabito and Makomo. In turn, Tanjiro works hard to earn their respect and is extremely grateful for the training and protection they provide him. During the Final Selection, Tanjiro is motivated to defeat the Hand Demon not only to save his own life but because it killed so many of Sakonji's other students. Once Tanjiro defeats the demon and returns to Sakonji, the spirits of the deceased students can finally rest. This is a gift that Tanjiro is able to give to the found family that has done so much for him.