Demon is an American supernatural action comic by Jason Shiga. The comic, which follows a man who apparently cannot die, was self-published from 2014 to 2016 as a mini-comic and webcomic, then released as a four-volume, 720-page graphic novel by First Second Books in 2016 and 2017. It was unusually well-organized for a webcomic, having been entirely written and laid out before its release, with a well-founded story, consistent art, and daily updates.

The comic was received favourably by critics, who praised the clever story; its puzzles and plot twists; the artwork, which balanced the often grim subject matter; and the surprising humor. The comic won an Eisner Award and an Ignatz Award.

Jimmy Yee repeatedly kills himself and reawakens at a motel. The police misidentify him and suspect him of murdering motel guests. Jimmy concludes that he is a "demon", and that each time he dies, his mind possesses the closest person.

Agent Hunter of the OSS^{[lower-alpha 1]} takes custody of Jimmy. Jimmy attempts to provoke a suicide by cop, attacking Hunter, but is overpowered. Hunter locks the fatally injured Jimmy in a supermax prison death row cell so that Jimmy will possess the neighbouring inmate. Jimmy improvises a weapon and suicides through dozens of condemned prisoners until he reaches a guard and escapes.

Jimmy plans to kill an imprisoned drunk driver to avenge his family. The OSS set a trap, but both parties are surprised to find that Jimmy's 10-year-old daughter, Sweet Pea, is a demon possessing the brain-damaged drunk driver. Jimmy kills his way through the agents and escapes. He threatens to destroy the OSS if Sweet Pea is not brought to him. Hunter attempts another trap, but Jimmy kills the entire group and reunites with Sweet Pea. Hunter tricks Jimmy into making a disadvantageous possession and captures him.

It is explained that the OSS had a plan to make demons to replace hostile dictators with US puppets. However, project leader Dr. Gellman used the demonizer on himself and then killed his coworkers. Jimmy is offered a pardon to kill Gellman, who they say plans to attack the US. Jimmy agrees, but goes rogue and provokes a military response to destroy the OSS base. Everyone inside is killed, with Sweet Pea possessing her way out. Jimmy decides that he and Sweet Pea should quietly outlive any remaining adversaries.

After 90 years, Jimmy contacts Gellman. When they meet, Gellman kills himself, ending his long life; the next-closest person is Jimmy, another demon, who cannot be possessed.

Another 100 years pass. Jimmy is bored with life, feeling that the best is behind him. Jimmy unexpectedly walks into a trap set by Hunter, who had demonized himself before the lab was destroyed. Following an extended fight and chase, during which Jimmy phones Sweet Pea to warn her, Hunter executes Jimmy.

The OSS find Sweet Pea and imprison her at Osaka Castle, but she is able to send secret messages. Hunter plans to harvest Sweet Pea's blood over several months to make a demon army and replace world leaders. Six months later, he executes her and harvests her remaining blood to complete his army.

Jimmy finds himself conscious but sense-deprived. He reasons that he possessed an unborn fetus. Later, Jimmy is born, possesses an adult, and sends a message to Sweet Pea.

Seven months earlier, Sweet Pea receives Jimmy's warning that Hunter is still alive. She faces a dilemma: the only way to locate Hunter is to be captured, but if she is captured, she will not be able to fight Hunter. She recalls that each possession creates a parallel universe in which the suicide attempt failed. Sweet Pea possesses an astronaut and suicides in outer space, where the next-closest human is the same astronaut in a parallel universe. She goes to that universe's Earth and finds its Sweet Pea. One of them is captured, and the other receives the prisoner's messages and plans an attack. Months later, the free Sweet Pea receives Jimmy's message and they reunite.

Sweet Pea declares victory, but they both find life boring and decide to stop Hunter. They spend a month training, then create hundreds of duplicates using the entire human population in space. Hours before Hunter's scheduled world takeover, they launch their attack, with high casualties on both sides. The castle gate becomes a killing zone, and Hunter releases failsafes, killing friend and foe. Jimmy directly engages and overpowers Hunter, who orders the lab guards to reinforce him. Distracted, Jimmy is captured by Hunter.

Hunter wants Jimmy to witness his victory, but Sweet Pea has taken over the lab – their actual goal – and exsanguinated one hundred duplicates to demonize every human on Earth. Hunter's agents kill themselves in the planned coup, but there is no one left to possess. Hunter's last failsafes kill everyone at the castle and lab.

Far away from the battle, a Jimmy and a Sweet Pea watch news reports of the events. With everyone a demon and no one to possess, they are all equal and mortal. Sweet Pea is upset at this reality. Jimmy recalls that Gellman had said there was another way to make a possession, and considers the challenge of becoming a good person.

Cartoonist Jason Shiga began working on Demon in 2010^[1] when he had finished his previous title, Empire State.^[2] His earlier attempts at creating an epic work had both failed, and Shiga stated that his biggest obstacle to creating Demon was "figuring out how to do it" (emphasis in original). ^[3]

He usually spends as much time planning a book as he does drawing it,^[4] and it took him about three years to write and pencil 720 pages for Demon.^[2][5] In order to construct the puzzles and mathematics in his stories, Shiga wrote from the ending and worked backwards. He felt that he would "get completely lost and fizzle out otherwise."^[6] Shiga described the story as "a 3 player chess match that pivots into a series of 7 concentric escape puzzles [with] the chess match itself contained in 2 more layers of puzzles."^[7] Shiga sketched the sequence of scenes in reverse as well; this technique made him focus more on story than characterizations.^[5] Shiga cut some story arcs while thumbnailing,^[1] and rewrote the last chapter twice.^[2]

Shiga stated that the biggest influences on Demon were the Quantum Leap television series and the films Groundhog Day and Memoirs of an Invisible Man.^[5] Quantum Leap was his favourite show and inspired the possessions in the series,^[6] although he disliked that the leaps required performing good deeds.^[3] He was similarly disappointed with how good deeds broke the loop in Groundhog Day, feeling that there was no logic to it.^[2] Shiga was also inspired by MacGyver, whose title character used intelligence to overcome obstacles with minimal resources,^[1] and by Death Note, in which two brilliant minds compete for advantage.^[7][8]

The improvised weapon used to escape the prison was based on a real incident in Japan.^{[1][lower-alpha 2]} The final showdown at Osaka Castle was inspired by Shiga's visit there on his honeymoon. He was particularly influenced by an artist's interpretation of the Siege of Osaka in isometric perspective.^[1]

Shiga placed great importance on negative space in the layouts to control the pacing.^[5] The final art was inked in sequence,^[1] with coloring done in Photoshop.^[4] Although many reviewers have noted that Shiga's simple artistic style contrasts with the wild plots, making them more palatable, Shiga has stated that he did not consciously do this and is critical of his artistic skill,^[3] feeling that it is a professional shortcoming.^[4] He stated that he tried to make the scenes "tastefully depicted" given the material.^[3]

In 2013, Shiga submitted Demon to Abrams Books, which was publishing his previous title Empire State. It was rejected, Shiga later noted, due to his "crazy list of demands".^[2] Shiga was intransigent about the format and subject matter, and so decided to self-publish.^[9] Being solely responsible for production encouraged Shiga to "try every crazy idea I could get away with" – including issues of 4 pages, 60 pages, and one in which every panel was black.^[10][8]

Shiga initially released Demon as a mini-comic,^[1][7] which was a familiar format for him. He printed 400 copies of each issue^[7] on a Risograph printer,^[8] and mailed them out, believing that this would be the work's final form.^[1]

Shiga had been skeptical about webcomics;^[2] as an afterthought he put some pages on his website in January 2014, where it gathered a larger following.^[11][1] He decided to continue posting the webcomic as issues of the mini-comic were released. Having the story entirely mapped out made Demon unusually organized for a webcomic, allowing him to publish seven pages per week^[2] and to also display a completion bar indicating the comic's progress toward its conclusion.^[11] Shiga improvised a little while inking the mini-comic and webcomic, adding to some arcs and cutting others. This resulted in an additional 15 pages compared to his penciled manuscript.^[5]

He became an early adopter of Patreon and was receiving $2,000 per month^[2] by the completion of the webcomic on 23 May 2016.^[5] The earnings and readership convinced publishers that Demon was a marketable title. Shiga received offers and signed with First Second Books.^[2]

Demon is a supernatural action series.^[18] Shiga said that Demon is an homage to old superhero comics and to 1990s alternative comics.^[8]

In the science-fiction magazine Locus, Shiga wrote that the series was primarily "a story of a man obsessed with the application of logic and science to a seemingly inexplicable supernatural phenomenon." He likened Jimmy's path, from the squalid motel to a palace, to humanity's progress through the cumulative benefits of science and technology. Jimmy uses his reasoning and abundance of time to become the most powerful human in existence.^[19]

Shiga stated that immortality and the stability that comes from it allowed examination of what gives meaning to the life of the characters.^[6] Shiga has said that as a nihilist, he feels that there is no meaning to anything.^[2]