History TearJerker / DemonSlayerKimetsuNoYaiba

** In that flashback, we can see that Rui's parent were really not happy to murder their own son. As Rui's father is about to commit the deed, he states that they're going to die with him, showing that they were planning to kill themselves afterwards.

** Muichiro reunites with his twin brother in the afterlife and tells him how he was happy with is life and that protecting his friends with his life is not pointless.

** In that flashback, we can see that Rui's parent were really not happy on trying to murder their own son. As Rui's father is about to commit the dead, he states that they're going to die with him, showing that they were planning to kill themselves for what they were about to do.

* [[DarkAndTroubledPast Muichiro's past]], which is by far one of the most ''tragic backstories'' to have ever witnessed. When he was young, Muichiro had a family who were woodcutters, being born alongside his older identical twin brother, Yuichiro. When they were ten, they tragically lost their mother to bronchitis, while they lost their father who died falling off a cliff, trying to find medical herbs for his wife. Their deaths caused [[TookALevelInCynic Yuichiro to become cold, strict, and harsh towards Muichiro]], trying to drill out Muichiro's kindness. One day, when they were eleven, their home was attacked by a demon, who slashed off Yuichiro's left hand, [[BigBrotherInstinct trying to protect Muichiro]]. This drove Muichiro enraged and he began using every tool and log he had to brutally defeat the demon and watch as the demon was killed by sunrise. He later dragged himself to a dying Yuichiro, who begged the gods to spare his kind brother while they should punish him instead. Yuichiro later dies from his wounds and Muichiro had to spent the next days watching as his deceased brothers and himself were being eaten by maggots and he would've died if not for Amane and the Ubuyashiki children, who arrive just in time to rescue Muichiro. [[BreakTheCutie The trauma of losing his brother was so great that Muichiro began shutting himself off emotionally]] and [[AmnesiacHero losing his memories in the process]], becoming cold and distant just like his brother.

* Rui's past: when was a human, he was a [[DelicateAndSickly sick 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 planned to kill him, then themselves, but Rui felt betrayed and killed them first. This was what caused his obsession with familial bonds despite losing his memories. It's only in his last moments that he remembers it, and that his mother's last words were an apology for not giving him a strong body. Realizing his parents truly loved him all along, he regrets that his evil deeds will lead him to Hell, away from his parents. The truly tearjerking part comes right after, as Rui's spirit starts to descend into Hell; His parents' spirits come to him, declaring that they will always be together and [[YouAreWorthHell accompanying him to Hell]]. The sequence ends with Rui constantly apologizing to his parents as the three of them are engulfed in Hell's flames.

* After Tanjiro leaves the Rengoku house, Senjuro tells his father Shinjuro Kyojuro's message to take care of himself. Shinjuro finally puts the bottle of alcohol down and [[BreakTheHaughty starts mourning Kyojuro's death.]]

* Koetetsu. Just [[BreaktheCutie poor Koetetsu.]] The kid having to witness his uncle and friends being mangled up horribly by [[MadArtist Gyokko]] and then seeing that they are [[AndIMustScream still alive as Gyokko twists one of the swords causing one of the swordsmith to scream in pain]] is enough to make fans sadden, as they have to watch the poor boy crying tears seeing his friends' brutal demise. The worst part is that the kid is just 10 years old and he just had to witness one of the most grotesque deaths caused by a demon, who's clearly taking pleasure in Koetetsu's pain. This action is enough to enrage Muichiro.
-->'''Muichiro:''' Oi. You better knock it off, ''shitface''.
* After Tanjiro nearly kills Hantengu, he notices sun is rising. Hantengu's still alive... and then Nezuko starts burning.

--> ''Muichiro: "Oi. You better knock it off, '''shitface'''."''

* The ending song following the end of the Mugen Train anime adaptation, [[https://www.youtube.com/watch?v=jwriFosLRww&ab_channel=uyuutea Homura]] is widely considering as one of most '''inspiring but heartwrenching songs''' to ever listen to, mainly because how this song encompasses how much influence Rengoku had on Tanjiro.

** Mitsuri's reaction probably hurts the most. This is because Mitsuri was once Rengoku's tsuguko, and the two had a close sibling-like relationship. So once she receives news of her {{Cool Big Bro}}'s death, she looks greatly shock and horrified by the news.

* Koetetsu. Just [[BreaktheCutie poor Koetetsu.]] The kid having to witness his uncle and friends being mangled up horribly by [[MadArtist Gyokko]] and then seeing that they are [[AndIMustScream still alive as Gyokko twists one of the swords causing one of the swordsmith to scream in pain]] is enough to make fans sadden, as they have watch the poor boy crying tears seeing his friends' brutal demise. The worst part is that the kid is just 10 years old and he just had to witness one of the most grotesque deaths caused by a demon, who's clearly taking pleasure in Koetetsu's pain. This action is enough to enrage Muichiro.

* The reason why Shizunagawa brothers are such jerks? Sanemi has to kill his beloved mother after she was turned into a demon, and Genya blamed him for it, which hot them estranged. Then he joined Demon Slayers to avenge their family, and Genya joined too, to apologize one day to his brother,
* After Tanjiro nearly kills Hantengu, he notices sun is rising, Hanteng' still alive... and then Nezuko starts burning.
** Tanjiro couldn't choose between saving smiths or staying with his sister, so Nezuko launches him into the air, sacrificing herself. Fortunately she survived, and gained immunity to sunlight, but it was very close.

** Tanjiro couldn't choose between saving smuths or staying with his sister, so Nezuko launches him into the air, sacrificing herself. Fortunately she survived, and gained immunity to sunlight, but it was very close.

-->'''Teen:''' ''(weakly)'' Even though I...was able to...e-escape from that horrible...place...and make it...here...''(gasps)''...was it...not enough? Am I still...gonna die?

* Chapter 68: Shinjuro (Kyojuro and Senjuro's father) berating the former by saying he had no talent and that is why he died. When Senjuro starts crying his father tells him that Kyojuro's funeral is over and he should stop looking miserable. It is simply heartwrenching to see a father act this way towards his sons.

* In the immediate aftermath of Gyutaro managing to defeat all of the Demon Slayers (ending up with Tanjiro and Zenitsu blown off from the roof), Tanjiro crashes to the ground profusely apologizing for not managing to help everyone out (as he was already injured at the time). When he's knocked out, he's treated to a vision of Nezuko (inexplicably back as to when she was a human) scolding him [[https://tvtropes.org/pmwiki/pmwiki.php/Main/ApologisesALot for beating himself too much about it]], noting that he's been like that since their father died. It's a subtle way to show that, despite Tanjiro's determination and generally-optimistic nature, he has been carrying a lot of hurt and despair from his harsh life back in mountains, piled onto by his [[VengefulWidow crusade for his family]].

* Rui's past: when was a human, he was a [[IllBoy sick 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 planned to kill him, then themselves, but Rui felt betrayed and killed them first. This was what caused his obsession with familial bonds despite losing his memories. It's only in his last moments that he remembers it, and that his mother's last words were an apology for not giving him a strong body. Realizing his parents truly loved him all along, he regrets that his evil deeds will lead him to Hell, away from his parents. The truly tearjerking part comes right after, as Rui's spirit starts to descend into Hell; His parents' spirits come to him, declaring that they will always be together and [[YouAreWorthHell accompanying him to Hell]]. The sequence ends with Rui constantly apologizing to his parents as the three of them are engulfed in Hell's flames.

* When Nezuko turns into a demon at the beginning of the series, the first thing she does is attack her brother. Tanjiro, who's barely holding her back with the handle of his axe, [[IKnowYoureInThereSomewhereFight can only tearfully beg her not to give in and become the bloodthirsty monster all other demons are]]. And it ''works'', since Nezuko relents... and [[BrokenTears also starts crying]], pictured to the right; She ''really'' didn't want to hurt her brother, [[MyGodWhatHaveIDone but her newfound hunger for flesh almost drove her to do something horrible]].

* As if Kazumi's situation weren't bad enough already, a flashback reveals that he got the bruises on his face when his would-be father-in-law beat him up, blaming him for Satoko's disappearance. Most of the townspeople gossip about him with pity in their voices, so it's likely that Tanjiro was the only person who genuinely sympathized with Kazumi after Satoko's disappearancee.
* When Tanjiro tries to comfort Kazumi, Kazumi lashes out at Tanjiro, [[InnocentlyInsensitive claiming that Tanjiro hasn't lost anyone important to him]]. But when Kazumi gets a glance at Tanjiro's hands, he immediately realizes the harsh training that Tanjiro, a mere child, went through, and realizes that Tanjiro must have suffered the pain of loss, too. He then immediately apologizes for his insensitive remarks.

* Susamaru was hardly a developed or sympathetic character, but as demons go she was one of the less loathsome, seeming more interested in the fun of battle than any sadistic motives. Her CruelAndUnusualDeath by Muzan's curse was absolutely brutal, moreso than many more unlikable demons' deaths, and when she's been reduced to an indistinct pile of meat, she's still alive until the sun comes up, with her mind seeming to have regressed to a state of childhood, asking for her temari ball and begging Tanjiro to play with her. Small wonder Tanjiro calls Muzan a monster who readily takes advantage of someone's loyalty for him, like he truly is as the series goes on.

* Kyojuro tells Tanjiro that he recognizes Nezuko as a Demon Slayer Corps member since she protected the humans on the train. Then he tells Tanjiro, Zenitsu and Inosuke that he believes they will become great Hashira. This makes Kyojuro's death even more heartwrenching as the three boys cry uncontrollably after he passes away.
* Inosuke tries to motivate the other two boys to stop crying and go training, stating that if someone dies they return to the earth and cannot come back. Despite him trying to act tough and say he is not crying, he clearly can be seen crying through the mask.

** As Daki and Gyutaro are dying, they start bickering with each other and blaming each other for how they ended up like this. Daki does the unforgivable and for the first time, she presses Gyutaro's complex about his appearance, angrily wondering how did an ugly person like him becomes her brother. Seeing such ungratefulness in front of him, Gyutaro snaps, angrily retorting that he sacrificed everything to give her a better life and he wouldn't face such difficulties had he left her for dead, which leave Daki stunned and looked like she was about to cry or take back what she said. Tanjiro finds this painful to watch, and tells them that they should at least care for each other, since no one else will forgive what they have done or mourn their deaths.

** As Daki and Gyutaro are dying, they start bickering with each other and blaming each other for how they ended up like this. Daki does the unforgivable and for the first time, she presses Gyutaro's complex about his appearance, angrily wondering how did an ugly person like him became her brother. Seeing such ungratefulness in front of him, Gyutaro retorts that he sacrificed everything to give her a better life and he wouldn't face such difficulties had he left her for dead, which leave Daki stunned and looked like she was about to cry or take back what she said. Tanjiro finds this painful to watch, and tells them that they should at least care for each other, since no one else will forgive what they have done or mourn their deaths.