- As monstrous as the demons could be, some of them have tragic pasts that will incite tears.
- When Rui was a human, he was a sickly child whose parents asked a doctor (actually Muzan) to grant him a strong body. He got turned into a demon and started eating humans. Realizing their mistakes, his parents tried to do a murder-suicide to him, but Rui felt betrayed and killed them first. This was what caused his obsession with familial bonds despite losing his memories. It was only at his last moments that he remembered it, and that his mother's last words was an apology for not giving him a strong body. Realizing his parents truly loved him all along, he regretted that his evil deeds would lead him to hell, away from his parents. The truly tearjerking part comes right after, as Rui's spirit started to descend to hell, his parents' spirits came to him, declared that they will always be together, accompanying him to hell. The sequence ends with Rui constantly apologizing to his parents as the three of them got engulfed in hell's flames.
- Daki and Gyuutarou were truly evil demons who killed countless numbers of people, but their sibling bond is genuine. Gyuutarou was a hideous kid who is hated by everyone, even his own mother. It was only after his sister Ume (which would later became Daki) was born that he found happiness. Ume started to work as a geisha while Gyuutarou became a debt collector. One day, however, a customer tried to assault her and she countered by stabbing his eyes. This caused her to get burned to death while he was away. Enraged at this, Gyuutarou accepted Douma's offer to become a demon, only so that he can be with sister again and to get back at the unfair world that made them suffer. In his last moments, he regretted how she ended up, imagining she could have lived much better lives if she weren't related to him. During the afterlife sequence, while he was preparing to go to hell, he shooed Daki away, telling her to go the "place with light", hoping she could still have a chance at redemption. This only caused her to cry and apologize for being weak. She stuck to his back, not wanting to separated from him, saying that they will always be together, and that she would still be his sister even after reincarnation, all while crying violently as the two walked to hell.
- Akaza has one of the most tragic lives in the manga. Born as Hakuji, he lived in poverty with a sickly father. This forced him to pickpocket and commit crimes from a very young age to obtain money for his father's medicine. His filial piety was not rewarded, however, as his father committed suicide so that he would not be a further burden and Hakuji could live an honest life. During his mourning, he got into a brawl and was scouted by a martial artist. Things began to start looking up when he was accepted as a disciple, and he even fell into a mutual love with the master's daughter. His happiness didn't last long, as some rivals who wanted their dojo poisoned the waters, killing his new family. Enraged, he charged into the rivals' dojo, brutally slaughtering every one of them. Muzan found him shortly afterward. Amazed at his strength, he forcibly turned the broken Hakuji into a demon. Losing his human memories, as the demon Akaza he once again started pursuing strength, which he then realizes was meaningless as he no longer has anything to protect. However, the spirits of his father, master, and lover manage to reach out to Akaza and convince him to return back to normal. In the end, Akaza returns back into Hakuji and tearfully embraces his lover, repeatedly asking for her forgiveness for not being able to protect his loved ones. She was just glad that he remembered them and tearfully welcomed him back, also embracing him closely.
- Tamayo is revealed by Muzan in their confrontation to have eaten her own family when she turned into a demon, and then ate other humans in despair for a period. Worse, the only reason she became a demon was because she was dying of an incurable illness and wanted to see her children grow up. Knowing this makes her tears when Nezuko hugs her far sadder in hindsight; she was likely thinking of her own children.
- Zenitsus life was filled with self-doubt and wrong turns, he was always looking for a place to belong, to really feel someone loved him; it was by accident that Zenitsu got taken into the world of demon slaying by the chance encounter with the elder known as Jigoro Kuwajima, Zenitsu seemly hated training as he felt no progress was made at all, Zenitsu felt like a failure, he wanted to run but Jigoro did his best to steer Zenitsu into the path of the Breath of Thunder, even with all his incessant bawling Zenitsu realized his master Jigoro was the first person to ever truly stick by him, so the news about his seppuku devastated Zenitsu, Jigoro died alone to atone for his other pupil betraying the corps to become a demon, Kaigaku was the cause but even so Zenitsu had some degree of respect for his colleague but Jigoro committing suicide to atone was just too much, Zenitsus newfound resolve eventually made him triumph over Kaigaku, the once perceived superior disciple, but the real win in Zenitsus path was his master himself telling him on the way to the afterlife that Zenitsu was his pride and joy, Zenitsu truly found someone who had loved him, the chance meeting that changed his life for the better, even if tears were to be shed along the way.
- Inosuke comes to aid Kanao just in time to protect her. When he sees her hurt, he chides her for not being careful and that Shinobu will get mad. It's only due to her sorrowful stare that he realizes Shinobu is dead, causing him to remember that time when the older girl took care of him and bonded with him with a pinky promise. Needless to say, Inosuke is pissed.
- Inosuke's mother, Kotoha, turned out to be a pitiful woman who loves her child deeply but was so unlucky that, even after a lifetime of abuse and being used by bad people, she couldn't even die in peace. She was eaten while fearing for her baby whom she was forced to throw down a cliff just so he could escape a demon.
- After Douma's defeat, Inosuke and Kanao had a moment to reflect on themselves. Inosuke remembered that his mother really did love him when he was young and softly cries for her. Meanwhile, Kanao searches desperately for the hairpiece that belonged to Shinobu. She reflects on her experiences. In her childhood, she wasn't able to cry because of her harsh childhood and tells that she did everything Shinobu said to make her own life better, such as making friends who helped her out in return. She manages to find Shinobu's hairpiece and the spirits of Kanae and Shinobu give her encouragement before happily moving on to heaven, where they reunite with their mother and father, happily embracing one another. Kanae finally cries and expresses her emotions. The next chapter shows both Kanao and Inosuke letting their tears run down their face.
- In the fight against Kokushibou, he cuts off the limbs of Muichirou and Genya, soon about to finish off Genya with one slash. However, Sanemi breaks through the ceiling to save his brother. He later reveals that the way he acted towards Genya wasn't out of hatred over Genya calling him a monster, but out of brotherly love. He wanted to keep Genya away from the Demon Slaying Organization so that he could find a happier life for their family and for himself. Genya, realizing that Sanemi loved him all this time, tearfully apologizes to his big brother. Sanemi is absolutely pissed and is fueled with great anger towards Kokushibou for injuring his brother.
- Sanemi's motivation was shortly revealed after. In a flashback, it shows Sanemi having to fight demons on his own with whatever tools he could find before befriending a Demon Slayer and joining the organization. The two bonded together and became best friends. However, after defeating a Lower Moon, Sanemi had lost his friend due to critical injuries. The day after, Pillars are called for a meeting and Sanemi starts accusing Ubuyashiki of being cowardly and viewing him and the other Demon Slayers as cannon fodder. Ubuyashiki calmly apologizes to Sanemi and explains that he truly wished he could join his fellow Demon Slayers, but due to his weak body, he could not perform the training to do so. He also saw himself as cannon fodder and soon revealed that his son would continue on in his place should he ever fall in battle. And he reveals that he always remembered the names of the fallen Demon Slayers, including Sanemi's best friend and loved them all equally. He gives his best friend's will to Sanemi, which reveals that his best friend saw his own brother in Sanemi and only wanted his brother to live a happy life. This moves Sanemi to tears and thus became his enitre motivation to keep his own brother Genya safe and sound.
Tear Jerker / Demon Slayer: Kimetsu no Yaiba