Slayer X Family
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1000 Origami Cranes by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
29 Mar 2024
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Summary
Everyone has a secret self they don't show to others.
Not to friends, not to lovers, not even to family.
With lies and fake smiles, they hide their true self.
And so...
THE WORLD MAINTAINS ITS THIN AND FRAGILE PEACE.
A oneshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Series
- Part 1 of Slayer X Family
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Fortune Tellers by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
17 Apr 2024
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Summary
A twoshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Muichiro does a school assignment on Sanemi's (cover) job. Muichiro, Sanemi, and Giyu go to the aquarium and Muichiro gets a giant stuffed penguin.
Series
- Part 2 of Slayer X Family
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Lotuses by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
30 Apr 2024
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Summary
A oneshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Muichiro is put in the same group as Rui for a paper focused arts and crafts class and uses it to help their friendship. The next day, Muichiro has a friend over.
Series
- Part 3 of Slayer X Family
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Butterflies by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
07 Jun 2024
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Summary
A twoshot of an SXF-inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Giyu takes lessons on cooking from his coworkers until he finally finds something he can cook for Sanemi and Muichiro. The day after he cooks for them, Muichiro goes to school and sets off for a field trip with his class when their bus is hijacked.
Series
- Part 4 of Slayer X Family
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Ice Crystals by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
23 Jul 2024
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Summary
A threeshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Muichiro, Sanemi, and Giyu go on a ski trip to the Kiyomi Mountains, a mountain range owned by Kimiko's family. When a blizzard hits, the three of them sleep in an inn for the night where attempted murder takes place...
Series
- Part 5 of Slayer X Family
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Birds by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
25 Aug 2024
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Summary
A oneshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
The Shinazugawa family's peaceful evening is interrupted by an unexpected nuisance.
Series
- Part 6 of Slayer X Family
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Paper Hats by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
07 Sep 2024
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Summary
A twoshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Giyu leaves for a few days on an important job. Sanemi and Muichiro have a visitor over in the meantime.
Series
- Part 7 of Slayer X Family
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Autism by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
21 Oct 2024
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Summary
Being neurodivergent, Muichiro's brain is of an alternate neurotype than the general, or, neurotypical population. This makes him different, and poses many challenges in his everyday life, trying and struggling to play by the rules of a world not built for him.
(I know I've hinted at his autism in this series multiple times now. This threeshot will be a bit more focused on it.)
(The only part so far of Slayer X Family to not be named after origami.)
A threeshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Series
- Part 8 of Slayer X Family
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Snakes by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
09 Nov 2024
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Summary
A oneshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Muichiro gets very sick and has to miss school. When Giyu is away and Sanemi is very busy, Sanemi brings an unexpected babysitter...
Series
- Part 9 of Slayer X Family
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Cranes by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
10 Dec 2024
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Summary
A threeshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
After exam week comes to a close, the students look at their scores. There will always be those who score the highest, and those who score the lowest. And sometimes, those who fall under the latter category will attempt to drag the former down.
Or, a certain bully at school targets Muichiro, with the goal of completely ruining his life.
Series
- Part 10 of Slayer X Family
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Bears by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
22 Dec 2024
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Summary
A twoshot of an SXF inspired, Muichiro-centric, alternated universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Grade 7 students at Kimetsu Academy go on a field trip to the zoo known as Wild Wonderland. It doesn't go as planned.
Series
- Part 11 of Slayer X Family
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Bookmarks by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
15 Jan 2025
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Summary
A threeshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Muichiro goes to Central Library, finding Rui there. The next day, they study together.
Series
- Part 12 of Slayer X Family
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Dragons by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
01 Feb 2025
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Summary
A oneshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
The bullying from Kaigaku's group gets worse as they aim to completely ruin Muichiro's life. Then, one incident changes everything.
Series
- Part 13 of Slayer X Family
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Jumping Frogs by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
23 Mar 2025
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Summary
A threeshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
A normal weekend in the Shinazugawa house becomes very... not normal, with storms and flooding. Still, they make the most of it.
Series
- Part 14 of Slayer X Family
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The Kiyomi Mountains by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
30 Apr 2025
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Summary
A threeshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
(The second part so far of Slayer X Family to not be named after origami.)
Muichiro, Sanemi, and Giyu go on a three day ski trip to the Kiyomi Mountains. Their plan is simple, to have fun skiing. But it becomes much more than a ski trip...
Series
- Part 15 of Slayer X Family
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Hearts by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
07 Jun 2025
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Summary
A fourshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Love is in the air at Kimetsu Academy as the gala approaches. An event like this just might be enough to cause students' true feelings to finally surface.
Series
- Part 16 of Slayer X Family
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Fans by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
25 Jul 2025
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Summary
A sixshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
When an extreme heat wave hits, Sanemi, Muichiro, and Giyu escape it on a coolcation to the western mountains, with Rui and Jeeves. They climb mountains, soak in hot springs, and almost get themselves killed when Sanemi is handed a mission to complete, Giyu finds himself face to face with someone seeking vengeance, and Muichiro encounters people he hasn't seen in a very long time, but could never forget.
Series
- Part 17 of Slayer X Family
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Slayer X Family: Author's Art by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
13 Oct 2025
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Summary
A compilation of artworks made for my series Slayer X Family. Mostly panels from Spy X Family redrawn as Slayer X Family. Enjoy!
Slayer X Family: A series exploring an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Series
- Part 18 of Slayer X Family
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Cats by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
06 Oct 2025
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Summary
A twoshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Muichiro, Sanemi, and Giyu choose to adopt a pet cat for Muichiro’s mental health. Chaos follows when they find themselves in the middle of a terrorist crisis that threatens to bring back a military conflict between Westalis and Ostania.
Series
- Part 19 of Slayer X Family
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Planes by KosmosTheUnderworlder
Fandoms: 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Manga)
14 Nov 2025
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Summary
A threeshot of an SXF inspired, Muichiro-centric, alternate universe where Sanemi is a spy, Giyu is an assassin, and Muichiro is their adopted telepath son.
Muichiro's school goes on a graduation trip to Hugaria. Sanemi and Giyu go along as parent chaperones. Muichiro runs into someone he hasn't seen in a long time, but could never forget.
Series
- Part 20 of Slayer X Family