Tanjiro Kamado: Amazing! You really are superhuman!!
Demon in the Temple: [screams]
Tanjiro: You really don't die, do you?!
Demon in the Temple: Stop it already!!
Giyu: The boy has gone insane. I know it's a hard request, but I would like you to raise him.
Urokodaki: Giyu, I have come to understand why nobody likes you.
The webcomic loosely adapts the source material, the main difference being that Tanjiro Kamado becomes the Black Swordsman that terrifies even demons after losing not only most of his family but also his eye and arm. And gone completely insane.
It was serialized on Twitter since April 21, 2020 and on Pixiv since May 9. Osker originally scheduled the webcomic to end with a total of twenty-two chapters, but the Twitter version ended with a total of twenty-three chapters.
What If I Know Too Many Reasons I Can Be Strong? provides examples of:
- Adaptational Badass: Tanjiro is much stronger than his canon counterpart, from dividing the boulder just in thirty minutes during his training to terrifying even Muzan like how Yoriichi did.
- Adaptational Curves: Tanjiro becomes larger and more muscular than his canon counterpart after the Time Skip.
- Adaptational Jerkass: Tanjiro lacks the defining compassion of his canon counterpart, physically or emotionally torturing demons without remorse. In the Pixiv version, he even says self-righteously that death means salvation for demons after killing Nakime while his canon counterpart solemnly prays that one of the demons he kills won't become a demon again in the next life.
- Adaptational Nice Guy: Muzan starts out as the same monster as his canon counterpart, not only killing most of Tanjiro's family in an attempt to make more demons but also taking his eye and arm away. However, Tanjiro nearly killing him in Asakusa and successfully killing most of the Upper Ranks humble him enough that he lets go of Kokushibo and Akaza, the only remaining members of the entire Twelve Kizuki, and thanks them for serving him for a long time.
- Adaptation Distillation: The webcomic skips most of the First Mission, Asakusa, and Functional Recovery Training arcs, leaving only Tanjiro's encounter with Muzan in Asakusa and the meeting of the Hashira.
- An Arm and a Leg: Tanjiro loses his left forearm much earlier than in canon in Chapter 1.
- Artificial Limbs: Haganezuka makes Tanjiro a prosthetic forearm.
- Ax-Crazy: As Giyu notes Tanjiro's insanity, the first chapter depicts Tanjiro viciously torturing the demon in the temple with an ax after Muzan kills most of his family in front of him, takes his left arm and right eye away, and turns his surviving sister into a demon.
- Beyond the Impossible:
- In the Pixiv version of Chapter 11, Tanjiro kills Nakime by stabbing her in the back rather than by decapitation, the latter of which is one of the only ways to kill demons.
- The Pixiv version of Chapter 19 reveals that Nezuko has killed Kokushibo just by punching him in the face.
- BFS: Haganezuka makes Tanjiro a huge sword named the Demon Slayer.
- Bittersweet Ending:
- Muzan and most of the other demons (except for Tamayo and Yushiro) are now dead and nearly everyone survives their canonical fates, but Tanjiro is revealed to have become a demon just like in canon and kills himself to stay human and be with the rest of his mostly dead family.
- Played For Laugh in the last chapter of the Pixiv version as a Bait-and-Switch
- Blood from the Mouth:
- Akaza bleeds from the mouth when Tanjiro taunts him about his past at the end of Chapter 6.
- Kokushibo not only bleeds from the mouth but from the nose when Koyuki's ghost punches him in the cheek at the end of Chapter 19.
- Bullying a Dragon: Sanemi stab Nezuko just like in canon... except Tanjiro here is now a raging berserker swordsman wielding a massive sword and have a built-in cannon in his left arm prosthesis. Take one guess what happen next.
- Compressed Adaptation: The webcomic skips the Drum House and Natagumo Mountain arcs entirely.
- Curb-Stomp Cushion: Akaza and Kokushibo hold their own against Tanjiro and are able both give and put up a decent fight even with him in Yoriichi Type Zero. Considering that his battles against other demons — including other Upper Ranks like Doma — have been rather one-sided, this is quite an impressive feat that makes it fitting for their status as the strongest members of the Upper Ranks in the first place.
- Death by Adaptation:
- Death by Irony: Kokushibo used to be nothing but Yoriichi's caring brother, only to turn into a demon out of jealousy for Yoriichi's exceptional talent. Tanjiro in Yoriichi Type Zero kills him with the flute he made for his brother to blow for help.
- Demoted to Extra: Sabito is one of Tanjiro's mentors in the original manga. The Pixiv version of the webcomic, however, demotes him to a cameo since Tanjiro is much stronger than his manga counterpart.
- Disabled in the Adaptation: Tanjiro loses his right eye and left forearm earlier than in the original manga.
- Enemy Mine: Tanjiro and Muzan are forced to do this against a berserk Nezuko.
- Establishing Character Moment: Tanjiro establishes himself as an Ax-Crazy Adaptational Jerkass by torturing the demon in the temple with a Slasher Smile, instead of hesitating to harm him, after Muzan kills most of his family in front of him, takes his left arm and right eye away, and turns his surviving sister into a demon in the first chapter.
- Eye Scream: Muzan transfers his blood to Tanjiro, destroying the latter's right eye. The final chapter reveals that Tanjiro's demonic transformation has restored his right eye, though it has a slit pupil instead of a normal one.
- Expressive Mask: When Nezuko briefly gains a cleft chin in Chapter 18, Urokodaki's mask moves its eyebrows and mouth with surprise.
- Glowing Eyes of Doom: Chapter 12 depicts Tanjiro as a silhouette with a glowing eye as Muzan talks to Kokushibo and Akaza about how he's slain Doma, Hantengu, Gyokko, and Nakime.
- Handicapped Badass: Losing an eye and arm doesn't stop Tanjiro from dividing the boulder just in thirty minutes during his training under Urokodaki.
- He Who Fights Monsters: Tanjiro is as vicious as the demons he hunts. The final chapter reveals that Nezuko, who bears no ill will against Tamayo or Yushiro, attacked him several times because she recognized him as a demon not only in body but also in mind.
- Horrifying the Horror: Tanjiro terrifies every demon he encounters, including even Muzan and the Twelve Kizuki. More often than not, it is mostly Played for Laughs.
- Hunter of His Own Kind: Tanjiro hunts demons just like in canon, but he's utterly devoid of his canon counterpart's compassion. The final chapter reveals that Muzan has turned him into a demon in the first place.
- Killed Offscreen: Tanjiro kills Doma, Hantengu, and Nakime between the Twitter versions of Chapters 11 and 12.
- Love Redeems: Akaza chooses to be with Koyuki in death instead of staying with "those disgraceful demons" in life.
- Mythology Gag: The title of the webcomic references the beginning lyrics of "Gurenge" from the anime adaptation of the original manga.
- Haganezuka still goes berserk whenever one of his swords get damage, especially if it get broken in two.
- Not So Different: In the final chapter, Tanjiro tells Nezuko that his vicious treatment of demons makes him little different from Muzan, who not only killed most of his family but also took his eye and arm away.
- Screw This, I'm Outta Here!:
- Muzan escapes when Tanjiro is about to attack him with the Demon Slayer sword in Asakusa.
- Muzan tries to run from Tanjiro, only to be taken Up to Eleven when a rampaging angry Nezuko pursues both of them.
- To Berserk:
- Tanjiro has Guts' black clothing, huge sword, and muscular build.
- Haganezuka names Tanjiro's sword the Demon Slayer.
- Chapter 5 has Tanjiro escape the Lotus-Eater Machine by quoting Guts to his past self.
- The Red Light District arc has Tanjiro say he's to sell himself for three silver coins, the same price as when Gambino pimped Guts as a child.
- Chapter 11 reimagines Yoriichi Type Zero as the equivalent of the Berserker Armor.
- In the Pixiv version of Chapter 11, Tanjiro kills Nakime the same way Sephiroth does to Aerith in Final Fantasy VII. Doma tells him afterward, "[she] will no longer talk, no longer laugh, cry... or get angry... What about me... what am I supposed to do? What about my pain?".
- In the Pixiv version of Chapter 18, Kokushibo screams at Tanjiro, Muzan, and Akaza "In the Name of the Moon, I will punish you all! Moon Prism Powerrrrrr?!!", referencing the Catchphrase and transformation phrase of Sailor Moon.
- To Berserk:
- Slasher Smile: Tanjiro tortures the demon in the temple while sporting a sadistic grin.
- Spared by the Adaptation: It's implied that Tanjiro' actions save almost everyone from their canonical deaths.
- Telepathy: The final chapter reveals that Tanjiro's demonic transformation has given him the ability to read not only the minds but also the forgotten memories of demons. This explains why he could taunt his enemies about their former human lives.
- Time Skip: The webcomic skips two years after Giyu's letter to Urokodaki.
- Title Drop: The webcomic ends with Tanjiro killing himself as he remarks that he's known too many reasons he can be strong.
- Titled After the Song: The title of the webcomic references the beginning lyrics of "Gurenge" from the anime adaptation of the original manga. The motion comic adaptation plays the instrumental version of the song during the credits.
- Took a Level in Kindness: Muzan starts out as the same monster as his canon counterpart, not only killing most of Tanjiro's family in an attempt to make more demons but also taking his eye and arm away. However, Tanjiro nearly killing him in Asakusa and successfully killing most of the Upper Ranks humble him enough that he lets go of Kokushibo and Akaza, the only remaining members of the entire Twelve Kizuki, and thanks them for serving him for a long time.
- Used to Be a Sweet Kid: Tanjiro is a ruthless warrior who has no qualms about torturing demons. His dream implies that he used to be a Nice Guy just like in canon before Muzan kills most of his family in front of him, turns Nezuko into a demon, and takes his right eye and left arm away.
- Wouldn't Hit a Girl: In the Pixiv version, Akaza refuses to help Tanjiro and Muzan against Nezuko because of his code against harming women. This gets him killed.
- You Are Already Dead: The Hand Demon gloats about having eaten Urokodaki's mentees, only for Tanjiro to reveal that he's already been decapitated.
- Younger Than They Look: Tanjiro is only fifteen after the Time Skip, but he looks more like a huge muscular man.
- Your Head Asplode: Tanjiro kills Kokushibo by exploding his head with the flute he made for his brother to blow for help.