Atomcat (アトムキャット) is a spin-off of the Astro Boy series. It was first published in Japan in 1986. It was released in English by Digital Manga Publishing in 2013. The title is a pun of “a tom cat”.
In this story, Astro Boy, named Tetsuwan Atom (as his name was left untranslated), is a fictional character with his own comic. The Atomcat story sometimes shifts to tell tales about the original Astro Boy, although they are always relevant to the plot at hand.
Tsugio and his father are big fans of the comic book called Tetsuwan Atom, even having inspired the father to make robots and other inventions of his own. Being a bullied child, Tsugio loved to read these comics and fantasize about having a friend like Atom whom could protect him from those bullies.
Eventually, Tsugio brings a dying cat home which he had found during the last encounter with his bullies. Bringing the cat back to health, Tsugio names the cat Atom. However Atom turns out to be a trouble maker, and so has to be taken away. While Tsugio and Atom are traveling to relocate the latter, Tsugio’s bike brakes fail and is hit by a car. The drivers turned out to be aliens disguised as humans, honeymooning on the Earth. Although the crash only gave Tsugio minor injuries, the impact had killed Atom, and so not wanting to get in trouble, the aliens brought the 2 and the bike to their spaceship.
The aliens have no idea about cat anatomy, and so scan Tsugio’s memories, discovering vivid memories of the fictional comic book character Atom is named after. Mistaking them for one and the same, the aliens bring the cat back to life as a cat with all the powers of Tetsuwan Atom, repair the bike, then put them where they were found.
After discovering the newly reborn Atom, Tsugio is surprised and excited, his wish for a protector has come true and Atom prevents the bullies’ next attempt at bothering Tsugio, but the two decide to keep Atom’s new found powers and ability to talk a secret, as it’s unusual for a cat. Soon after, Atom helps clear the rubble of Tsugio’s house that had been caused by a propane tank explosion.
Tsugio reads the tale of when Tetsuwan Atom was given to the circus because he cannot grow, soon overhearing his parents commentating on how Atom, the cat, doesn’t seem to be growing at all. However, this is not the only strange thing about Atom. Tsugio tries to discourage Atom from his immense cleanliness and other traits unusual for a cat.
Later on, Tsugio has another encounter with his bully, Gadaffi, but he quickly escapes and clumsily bumps into Erica, a girl whom soon becomes Tsugio’s new friend. When Tsugio finds out Erica’s cat, named Munch, is missing on Mount Otafuku, he asks for Atom’s help to find her. After Tsugio gives Atom a belt like the fictitious Atom, he goes out and does just that, along the way saving many other animals from a forest fire and developing a crush on Munch. However, Atom’s request for Munch to become his girlfriend is rejected when she states she’s only into ordinary cats, causing Atom to start to wish he were once again just a normal cat. When Munch is returned to Erika, Tsugio finds out that Gadaffi is Erica’s older brother.
The story story ends with Tsugio and Atom each getting a thank you gift, resulting in them feeling the day wasn’t so bad after all.
A mysterious woman named Matatabi appears with an equally mysterious Angora cat, she introduces herself to Tsugio’s mother, however Atom is uncomfortable about the presence of the Angora cat. Atom goes to warn Munch about this, but he appears out of nowhere, introducing himself as Mephisto, and proceeds to harm Atom. However, Mephisto is stopped when Tsugio’s father attempts to stop the racket they are making by throwing multiple objects at him.
Tsugio’s father has recently finished yet another one of his inventions: a robotic hand that acts as protection from burglars. However, when Tsugio’s mother tests it and it’s defense is affective, this angers her and she begins chasing Tsugio’s father around the house, accidentally smacking the head off of the mysterious woman who had came over once more. Tsugio’s mother begins to panic when she thinks she’s killed someone and panics further when it turns out the woman is a mannequin that seems to be alive. It turns out Mephisto is trying to scare away Atom’s human family so he’ll have to move out with them, giving Mephisto the opportunity to take Munch with no one interfering.
Atom fights Mephisto, and tries to protect Munch, eventually using Tsugio’s father’s invention to his advantage. Mephisto is tricked into being knocked out cold by the invention.
The fictitious Tetsuwan Atom is congratulated by his friends for having such good grades. However, Shibugaki teases him by throwing away the report card. When Atom attempts to retrieve it, he is zapped by the power lines and his friends come to his aid. After having lost the report card, Shibugaki further teases Atom by saying he wouldn’t have had parents to show it to anyway, causing Atom to deeply long for parents of his own. As Tsugio reads this story, he feels sorry for the fictitious Atom, comparing that his own life is better off than the unfortunate robot’s. Tsugio then had gone to help find Atom, the cat’s, parents, as he felt connected to the comic’s situation. After an unsuccessful search, Tsugio further reads the comic to find out how the story handled it. In the story, Dr. Ochanomizu had built Atom some robot parents at Tamao‘s suggestion.
Inspired by the Tetsuwan Atom story, Tsugio goes to dig out one of his father’s inventions that happens to look like a cat. Atom immediately loves it after having received it. However, this invention is a bomb disguised as a maneki-neko statue. Tsugio’s father was showing a mock-up copy of it to someone at the Mudagane Commerce as a device for burglar prevention when it sat on top of a safe. However, the invention is rejected due to the high price Tsugio’s father was asking for. On his way home, Tsugio’s father witnesses Atom about to pull the maneki-neko bomb’s hand down. Immediately, he tries to stop Atom as this is the bomb’s trigger. Tsugio’s father just barely manages to stop Atom from triggering the bomb, however his actions cause it to fall into the sewers.
While Atom chases after the maneki-neko bomb in the sewers, Tsugio’s father is in a panic at the chance it may explode, promptly deciding the family should move away in case it does. Atom successfully gets the maneki-neko bomb outside of the sewers and retrieves its missing tail from the landfill it had emerged in. However, Atom does not know it’s a bomb and once again tries to pull its paw down again when he meets up with Tsugio. While no one was physically hurt, Atom is shocked and upset that what he called his mother is now gone. Tsugio reassures Atom that his mother is definitely out there somewhere.
Gadaffi’s father has found a document that says 500 years ago a band of pirates named the Murakami Navy hid their treasure on an island. As his father plans to go to this island by boat, Gadaffi asks if anyone wants to join them. However, he excludes Tsugio from this offer, returning to his bully attitude towards him. Tsugio, disheartened at home, is encouraged by Atom to go to the island on their own while following the boat. However, Tsugio protests to the idea of flying as he has a fear of heights, so Atom stuffs him in a bag on the way to the island so Tsugio will be be less scared.
On the island, Tsugio thinks he has seen a ghost. Elsewhere, Gadaffi’s group find that their boat has been greatly damaged. The latter decide to sail back home, believing the island is haunted. However, it turns out that the island isn’t haunted at all; the tricks had been created by birds who wished to protect their untouched home from humans, dogs, and cats. The birds do not believe Atom will keep their island safe, so they try to attack him, but Atom flees.
During the night, Atom goes back home to collect many pieces of chain link fencing and fences the whole island up. When the sun rises, the birds release this and panic, promising to give Atom whatever he wants. He asks for where the treasure is and then he and Tsugio will leave. Although the birds did agree, it appears the treasure was just a legend after all.
One of the fictitious Atom’s flaws is lack of creativity or humans’ perception of beauty; he only sees things simply as they are, even to the tiniest detail. He even preferred disorganized sound over music. He had began to feel upset by this difference between himself and humans. Since the fictitious Atom had trouble drawing, Tsugio wondered if things would be different for Atom, the cat; he attempts to get him to draw without much success. Atom felt guilty about running away from Tsugio’s attempts, especially since Gadaffi was there as he left, he hoped Tsugio wasn’t being bullied too much.
When Tsugio didn’t return home in time for dinner, his parents began to worry. Atom sets out with Munch to find out why he hadn’t returned home. The two travel to where Tsugio was last seen, finding the sketch Tsugio had drawn was torn to bits. After finding all the pieces they could, the only missing piece would have depicted the roof. Finding this suspicious, they land on the building’s roof, where they then find a shrine to Inari. However, soon after, Munch goes missing while there.
Unsuccessfully finding Munch, Atom decides to burst through one of the lower levels and ends up eavesdropping on some peoples’ plan to manufacture guns with goods smuggled from the Philippines. It was these people who took Tsugio and Munch, and they planned to do away with them after three days. Hearing of this, Atom promptly rescues the two and puts a stop to the gun production.
It turns out Atom can actually draw, offering to let Tsugio use his sketch after the police had asked Tsugio to draw a picture of the smugglers’ leader.
Gadaffi pranks Tsugio by giving him a box and telling him a mummified cat is inside it. However, it turns out it was a cat themed jack-in-the-box. Crying all the way home, Tsugio no longer has any interest in going to the pyramid exhibit he and his mother were planning to visit that day. However, he’s forced to go anyway. Having brought Atom along with him, Tsugio tells him to hide so the security guards can’t locate him. Choosing to hide in one of the mummy sarcophagi, Atom discovers that he can’t open it again, as the spirit of the mummified cat has sealed it and then asks to help take revenge on the humans. However, Atom refuses and bursts out of the sarcophagus after putting a hole in it with his jet feet.
Later that night, a mummified cat emerges at Tsugio’s home, asking his parents where Atom is. Terrified, Tsugio’s mother tries to call the police after telling the whereabouts of Atom. However, the phone line has been cut.
The mummified cat gets various mummified animal companions to help surround the work shed where Atom and Tsugio are located. The mummies begin attempting to destroy the shed, but Atom begins crushing them and covering them with glue. With only the mummified cat left, they try to take on Atom alone, but Atom makes short work of them when he crushes him with a vehicle. The mummified cat’s last words were a warning that someday, humans will betray Atom. However, he does not believe Tsugio would ever do such a thing.