Red, a young, orphaned boy with a grotesque, red left arm, was sold to the circus, but has no memories of his life prior to his purchase. Refusing to work as a performer, Red takes on odd jobs in exchange for food and a place to live, something that he manages very well despite his inability to move his left arm.
Despite his efforts, however, Red is largely ignored by the circus troupe, with the exception of a clown, Cosimov, who often blames and beats Red for his misfortune. Due to the arrival of a new, popular clown, his abuse at the hands of Cosimov begins to worsen as Cosimov loses his place as the most popular performer.
One day, after a show, Cosimov begins to beat Red. The ringmaster enters at the commotion, but Cosimov insists that he was trying to teach Red a lesson for lazing around. The ringmaster believes him and punishes Red by taking away his dinner.
That evening, Red lies in the snow to soothe his injuries. Another boy comes up to him and, realizing that Red is from the circus, asks him what his act is. Red shows the boy his arm and the boy runs away in fear.
Later, Red sees Cosimov enter the tent and crash around. After Cosimov leaves, Red enters to clean up the mess Cosimov made, knowing that if any of the props are missing he would be to blame. As he cleans up, however, a dog jumps out from its sleeping place and steals one of the balls. Red runs after it. He chases it until he collapses and begins to lose hope that he will be able to recover the ball. The dog drops the ball on Red's head, however, and Red realizes it wants to play. They play catch for a little while and the rage and hatred that Red feels begins to melt a little.
The next day, Red decides to ignore the dog, knowing that someday it will go away with its master and never return. Despite the lack of attention it receives, the dog continues to loiter near Red.
Cosimov then pulls aside Red and demands that he mix glass into the dogs food, knowing that if he kills the dog, he will the number one clown; the clown currently holding the position would not be able to perform, as the dog is his partner. Red refuses, however, even as Cosimov begins to viciously beat him. Just as Red begins to lose consciousness, he hears barking.
Red awakens and fears that the dog was killed while protecting him. He is relieved, however, to find the dog performing with its owner and assumes that he had merely hallucinated the barking. He watches the two perform and begins to feel isolated and lonely as he witnesses the love and trust between the clown and his dog. After the show, the dog approaches Red and, in his emotional turmoil, he kicks the dog. Shocked by what he has impulsively done, Red runs away.
Red does not see the dog for some time, but convinces himself it is for the better. One day, he sees the dog sleeping next to a heater and reaches out to pet it. It wakes up and is happy to see Red, licking his left hand. Red feels as if he has been forgiven. The dog is called to perform and leaves Red's side.
The next day, after doing some chores, Red sees the dog's owner sit by a tree, all alone. Red goes to investigate and finds the dog lying on the ground, clearly having been beaten to death. He begins to talk with the owner, but is unable to understand why he doesn't want revenge for something that Cosimov was clearly responsible for. As Red begins to cry, the man realizes that he was a friend of Allen's, his dog.
On Christmas Day, Red goes into town with the man, passing out flyers. As the clown performs, he suddenly invites Red to join him and his showmanship amuses the crowd. When Red holds out a hat for coins, the audience throws in what change they have and Red is shocked to have his skills recognized.
As Red is collecting coins, a red-haired priest asks Red for his name. Not having one, Red attempts to ignore him, but the priests persists and asks him if his name is Allen. When Red responds negatively, the priest warns him not to get close to a man named Mana.
After collecting money, Red returns to the clown and asks if he is called Mana. Giving an affirmative answer, Mana asks why Red wanted to know. After explaining about the priest, Mana suddenly becomes serious and runs off, looking around frantically. After a long search, Mana explains that the man may have been his little brother. Not giving up, Mana continues to search until Red is forced to push Mana out of the way of a carriage. He drags Mana to a park to clean up.
Mana attempts to make small talk, but Red is still clearly miffed about Mana's carelessness.Red notices the most striking feature of mana: His golden eyes. Mana suddenly tells Red that he is only seventeen. He claims that he woke up one day and looked at the mirror to find himself a middle aged man. He tells Red that he is looking for his little brother, but cannot find him, and that he is being chased by a man named the Millennium Earl and if caught, he will be killed. He fears that because he has suddenly become a middle-aged man, his brother will not recognize him, and so he began his life of wandering. Red says that perhaps Mana was abandoned by his brother. Mana does not respond, instead exclaiming over the beautiful sunset, but Red observes he looks as if he has been crying.
Upon returning to the circus, Red sees Cosimov and is filled with rage. When he accuses Cosimov of killing Allen, Cosimov ignores him and accuses him instead. As the other circus members begin to glare at him, Red is overwhelmed with hatred and hits Cosimov with a plank. Cosimov exaggerates his injury, drawing attention of the Ringmaster. The Ringmaster begins to beat Red until the plank breaks and tells the other members to throw Red into an animal cage. Knowing he is about to be abandoned and utterly infuriated, Red evades the others and rushes at Cosimov again, determined to kill him in revenge for Allen. He attempts to hit Cosimov with his left arm, but hits Mana instead, who has stepped in the way.
As Mana protects Cosimov, telling Red that he must not kill someone, Red turns his anger to Mana and is infuriated by his ever-present smile. He begins to beat Mana over the head with his left arm. Finally exhausted, Red stops and Mana tells him how lonely Allen was and how he wasn't able to do tricks at first. He thanks Red for being Allen's friend, but he should let all the tragedies stop. Red begins to worry about Mana's strange, broken speech patterns, and suddenly realizes that Mana's head is covered in wounds. Red is then dragged away by other circus members and to be thrown into a cage. After he is gone, the Millennium Earl appears with a group of akuma and begins to kill everyone in the circus. Mana, barely conscious, watches until the red-haired priest steps in to kill the akuma.
Meanwhile, Red is thrown into a cage with a carnivorous animal. Red is certain he will die until a yellow, round object flies in, knocking down the animal. It chews through the cage bars, allowing Red to leave. As he does, he comes across the priest again, who prepares to kill him until the flying ball intervenes. The priest lets Red go, but tells him that all this happened because of him and orders him to disappear. The priest leaves, but Red becomes concerned about Mana and runs back to the circus, despite knowing that he will die if he stays.
After hearing the news that everyone from the circus has disappeared, Red finds Mana, who is still covered in blood. Mana cheerfully greets him, calling him "Allen", and wondering where they should go next. Mana suddenly begins to wonder why he is traveling, and Red attempts to remind him of his missing brother. Red begins to wonder if Mana forgot because he hit him too much. Red begs Mana to take him with him, offering to remember Mana's goal for him. Mana continues to call Red "Allen", wondering how he grew so big and why he has no tail. Red goes with Mana, realizing that, just like Allen and Mana made him happy, his reason for living is to make Mana happy and he resolves to become Mana's "Allen".