Demon Core is both the real plutonium sphere that killed two Los Alamos physicists in 1945 and 1946 and the Japanese fan art meme of anime girls poking that sphere with a screwdriver.

Where did Demon Core come from?

The historical core came from the Manhattan Project at Los Alamos, and the meme format started on Japanese Twitter with @nibiqn's April 4, 2018 Touhou fan art.

What does Demon Core mean?

It refers to the nickname given to the deadly plutonium core after the Slotin incident, repurposed online as shorthand for the fan art joke of casually mishandling the sphere.

How do you use Demon Core?

Artists typically draw a character holding a screwdriver over a shiny silver sphere with a beryllium hemisphere above, referencing Slotin's 1946 mistake.

Is Demon Core still popular?

The format stayed active across both Japanese and Western fan art circles after the May 2021 crossover push by @HellOnEarthIII and @drab_makyo, and large explainer videos like Kyle Hill's keep introducing new viewers.

Demon Core

2018fan art / dark humor memeclassic

Published October 8, 2026

Demon Core is the nickname for a plutonium sphere from the Manhattan Project that killed two physicists in 1945 and 1946 criticality accidents, one caused by a slipped screwdriver. Starting in 2018, Japanese artists on Twitter and Pixiv turned the deadly incident into fan art of anime girls poking the glowing orb, spawning a lasting dark-humor meme format.

dark humor memes fan art memes japanese internet memes anime manga 2018 memes

Overview

Demon Core is both a real nuclear artifact and the dark-joke art format it inspired. The physical core was a 6.2-kilogram plutonium sphere used in Los Alamos criticality experiments that killed physicists Harry Daghlian in 1945 and Louis Slotin in 19461. The meme flips that grim history into cute illustrations of anime girls, often Touhou characters, cheerfully holding a flat-head screwdriver over a glowing silver ball while a beryllium hemisphere hovers above it2.

The visual template is tightly coded. A character leans over the sphere, grips a screwdriver exactly as Slotin did, and the composition hints at the half-second blue flash witnessed during the 1946 accident3. The humor hinges on the viewer knowing the real story: the artist draws the moment right before everything goes wrong. Variants expand the gag to idols, VTubers, and generic cute mascots, and the joke scales from single illustrations to short animated loops and comics4.

Gallery

Origin & Background

Platform

Twitter / Pixiv (Japanese fan art spread)

Key People

Unknown

Date

2018

The real-world catalyst dates to May 21, 1946, when Louis Slotin's screwdriver slipped during a criticality experiment at Los Alamos, dropping a beryllium hemisphere onto the plutonium core and giving him a fatal 1,000-rad dose of radiation1. The 1989 film Fat Man and Little Boy dramatized the accident with John Cusack playing Slotin, keeping the story in low-level circulation for decades.

The meme format emerged on April 4, 2018, when Japanese artist @nibiqn posted a fan art of Touhou character Aunn Komano using a screwdriver on the core, racking up over 300 retweets and 570 likes5. Two weeks later on April 18, 2018, artist @shirosato_town posted a similar piece with Touhou's Koakuma that drew over 220 retweets and 400 likes on Twitter6, with a matching Pixiv upload picking up more than 540 smiles7. These two posts set the Touhou-plus-screwdriver template that the rest of the fandom copied.

How It Spread

After the April 2018 Touhou posts, drawing characters experimenting with the Demon Core turned into a running Japanese fan art trend across Twitter, Pixiv, and niconico seiga throughout 20182. On December 17, 2018, nuclear historian @wellerstein highlighted the trend to English-speaking audiences in a tweet that pulled over 1,300 retweets and 1,600 likes8, giving Western viewers their first organized look at the format.

YouTube pushed the real history to a much wider audience in parallel. On October 13, 2017, the channel Qxir uploaded an early viral explainer that passed 920,000 views9, and on November 27, 2020, Kyle Hill published a documentary that cleared 6 million views within months10. In March 2019, Japanese YouTuber Karameru posted the comedic short 'Demon Core-kun,' which hit over 3.2 million views and anthropomorphized the sphere itself as a mischievous character11.

The meme crossed firmly into Western social media in May 2021. On May 6, Twitter user @HellOnEarthIII posted a fan art version that circulated widely12, followed on May 10 by a @drab_makyo tweet based on a 2020 Tumblr piece by user bepisode13. Those two posts, within four days of each other, pulled the Japanese trend into English-language art Twitter where it stuck as a go-to dark-humor template2.

Timeline

1946-05-21

Louis Slotin's screwdriver slips during a Los Alamos experiment, triggering the second fatal Demon Core criticality accident.

1989

Fat Man and Little Boy dramatizes the Slotin accident with John Cusack, keeping the story in pop-culture circulation.

2017-10-13

YouTube channel Qxir publishes an early viral Demon Core explainer that eventually passes 920,000 views.

2019-03-13

Japanese YouTuber Karameru uploads 'Demon Core-kun,' a comedic short that gathers over 3.2 million views.

2020-11-27

Kyle Hill publishes a Demon Core documentary that passes 6 million views and becomes a popular English-language reference.

2021-05-10

Tweets by @HellOnEarthIII and @drab_makyo push the fan art format into Western social media.

How to Use This Meme

The typical Demon Core piece shows a single character, usually drawn in anime style, posed over a shiny metal sphere with a flat-head screwdriver in one hand. Common conventions include a beryllium half-dome hovering above the core, a small blue glow or flash effect to reference the 1946 accident, and a casual or unaware facial expression that plays off how dangerous the setup actually is. Captions often skip explanation entirely, trusting viewers to recognize the setup.