Episode 1: Violet is a soldier in the Leidenschaftlich Army who served under Major Gilbert Bougainvillea, who she was utterly devoted to. However, Violet is injured after a mission which resulted in the loss of her arms, requiring them to be replaced with prosthesis. Colonel Hodgins, an old acquaintance of Gilbert, arrives to pick up Violet. He explains to Violet that the war they were fighting has ended and peace has come, though he is unwilling to tell Violet what happened to Gilbert. They leave for the capital city of Leiden, where Gilbert had already arranged for Violet to be adopted by the Evergarden family. However, Violet cannot adjust to civilian life due to her military indoctrination. Hodgins then decides to show Violet his business, the CH postal company which acts as a private mail and ghostwriting service and hires her as a postal worker. She then witnesses the Auto Memory Dolls of the ghostwriting department writing a letter for an illiterate man who wants to proclaim his love to someone. Violet then remembers that "I love you" were the last words Gilbert had told her. Wanting to know the meaning of the words, Violet asks Hodgins for her to join the ghostwriting department. Impressed that Violet has finally shown signs of acting on her own free will instead of on someone else's orders, Hodgins accepts Violet's request despite her not being an Auto Memory Doll.
Episode 2: Violet joins the ghostwriting department and meets its members: the veteran Cattelya, and the two rookies Erica and Iris. Under Cattelya's direction, Violet begins her training as an Auto Memory Doll, quickly learning how to use a typewriter. However, despite her technical proficiency, Violet is still incapable of understanding emotions. This comes to a head when she offers to write a romantic letter that ends up angering both the recipient and the client. Erica then confronts Violet about her motivations to become a Doll, but relents when Violet tells her about her desire to learn the meaning of the words "I love you." Iris suggests to Hodgins to fire Violet, but Erica comes to her defense, partly motivated due to her own insecurities about being a proper Doll. Hodgins decides not to fire Violet and gives her a new uniform, along with the brooch Gilbert had originally given to Violet, which Hodgins managed to recover. Violet is overjoyed at the return of the brooch, and agrees to attend a Doll training course. That night, Hodgins confides in Cattleya that he used to be friends with Gilbert, and that Gilbert is "never coming back."
Episode 3: Violet attends at the Auto Memory Doll Training School in order to become a true doll. There, she meets and befriends a girl named Luculia Marlborough. The next day, Violet and Luculia are assigned to practice their actual ghostwriting skills on each other. However, Instructor Rhodanthe is unimpressed with the way Violet ghostwrote Luculia's letter, informing her that letters are an instrument for communicating a person's feelings, and that letter she ghostwrote was unacceptable. Luculia decides to take Violet to her favorite spot atop a bell tower to show her the view, and it is revealed Luculia's brother is crippled from the war and is now a drunkard. However, Violet fails to pass the class while Luculia graduates with top marks. Luculia meets Violet again and offers to ghostwrite a letter to Gilbert, but Violet cannot find the words to say. Luculia then tells Violet how her parents died in the war and her brother feels guilty over failing to protect them. She wants to tell her brother that she's just glad he's alive and home, but likewise cannot find the words to say. Touched by Luculia's words, Violet manages to write a short and concise letter that effectively conveys Luculia's feelings to her brother. Upon being shown the letter, Instructor Rhodanthe allows Violet to graduate and Luculia helps her brother to the top of the bell tower to enjoy the view like they used to as children.
Episode 4: Iris receives a personal ghostwriting request from her hometown, but accidentally injures her hand. As a result, Violet is sent along with her to assist her in writing. Upon arriving, Iris is met by her parents, and her mother reveals that she was the one who sent the request in order to get Iris to come back to celebrate her birthday. However, Iris is frustrated when her mother admits she wants to use the party as a way to find a suitor for her. As Violet writes the party invitations, Iris specifically asks her not to send an invitation to a man named Emonn Snow, but Violet sends the invitation anyways. When Emonn appears at the party, Iris angrily retreats to her room. Violet then talks to Iris to figure out what's wrong, and Iris tells her that Emonn was her childhood crush, but he rejected her confession. The emotional pain caused by Emonn's rejection was what caused her to leave her hometown to become a doll. This causes Violet to realize that a love confession like Gilbert's must have required a great deal of courage to say. Violet then helps Iris write apology letters to all of the party guests, as well as her parents. Moved by the letter, Iris' parents allow her to continue working as a doll. On the way back to Leiden, Iris tells Violet that her parents named her after the flower of the same name, since she was born while they were in full bloom. This triggers a flashback in Violet, who remembers that Gilbert named her after the flower of the same name.
Episode 5: On the request of the military, Violet is sent to the kingdom of Drossel in order to write a public love letter for its princess, Charlotte, to Damian, the prince of the neighboring kingdom of Flugel. Violet's mission is crucial since Drossel and Flugel were previously enemies in the war and are arranging the marriage to cement the terms of the peace treaty. Despite Charlotte being anxious about the wedding, Violet writes the love letter, and Damian writes a letter back in response, but Charlotte does not appear satisfied with it. Charlotte later confides in Violet that she met and grew infatuated with Damian when she first met him, since he treated her as a person and not a potential wife. However, she's unsure of whether Damian reciprocates her feelings or not, since she could tell the letter he returned contained no emotion in it. Violet then gets an idea and arranges with Damian's doll to have Charlotte and Damian write their own letters to each other. This starts a heated but passionate correspondence between the two that entrances everybody in both kingdoms. The wedding goes as planned while Violet and Cattleya, who was Damian's doll, return to Leiden, though Cattleya notices Violet smiling. Upon returning, Violet encounters Gilbert's brother Dietfried, who expresses disbelief at how she became a doll and reminding her she had killed countless people, including many of his men.
Episode 6: Violet, along with a number of other dolls, arrive at the Shaher Observatory in order to help the scholars make copies of a number of rare books. Violet is paired with a young scholar named Leon, who initially dislikes her and dolls in general. However, he is impressed with how quickly she works, and begins to soften when he sees that she doesn't care about his background or upbringing as an orphan. He invites Violet to view Alley's Comet with him, which appears only once every two hundred years, and she accepts. While the two stargaze, Leon explains that his father was also a scholar at the observatory but disappeared on an expedition. His mother then left home to search for him and never returned either, causing Leon to resent them and the concept of love. Violet then tells Leon that she has no known blood relatives, but is completely devoted to Gilbert. It's then that Leon realizes Violet is in love with Gilbert. The next morning, Violet prepares to leave now that her job is complete. Leon sees her off, and tells her that instead of waiting at the observatory for his parents to return, he'll start traveling the world like Violet to go look for them. As Violet leaves, Leon wonders if he'll ever encounter her again.
Episode 7: Violet goes to assist a famous writer, Oscar Webster, in writing his next play. However, she arrives to find him a drunk recluse. Violet manages to convince Oscar to suspend his drinking while they work, and they begin writing the play. The play is about a girl named Olive who uses her power to summon magical sprites to defeat a beast, but in doing so sacrifices her ability and becomes stranded away from her home and father. Violet becomes curious about how the story will end, which Oscar hasn't decided upon yet. Violet then finds a parasol, triggering an angry outburst from Oscar. He then admits to Violet that he based Olive off of his daughter Olivia, who had died from illness, and he is trying to write the play as a way to cope with his grief over her loss. Violet then inspires Oscar with idea of Olive using her magical parasol to fly home. Oscar comes to terms with his daughter's death and thanks Violet. On the way home, Violet begins to suffer regrets over the people she had killed during the war, wondering how many happy endings she may have prevented. Upon returning to Leiden, Violet learns from Mrs. Evergarden that Gilbert is dead and confronts Hodgins. He admits that after their final mission, neither Gilbert nor his body could be found, but his dog tags were recovered, leading to the army presuming him dead. Violet remains in denial about Gilbert being dead and flees the post office in distress.
Episode 8: Violet heads over to the military headquarters to confront Dietfried about the truth of Gilbert's fate, and he confirms he is dead. Still in denial, Violet travels to Gilbert's mansion, where she finds his grave. Back at the post office, Hodgins leaves to go look for Violet. Violet then begins to recall her past with Gilbert, which started when Dietfried transferred her to his command as a child soldier. Despite his desire to raise Violet as a normal girl, Gilbert is forced by his superiors to put her on the frontlines due to her combat abilities. Violet proves to be instrumental in winning many key battles. During this time, Gilbert gave Violet her name and taught her how to read and write, and he eventually buys her a brooch as a gift. Some time later, Gilbert's unit is assigned to stage an attack on the enemy's headquarters, the success of which could mean the end of the war. Gilbert's unit suffers heavy casualties in the assault, but they are able to seize headquarters and signal the main force to attack. However, just as Gilbert sends the signal, he is shot by enemy soldiers, shocking Violet.
Episode 9: Violet attempts to carry a wounded Gilbert to safety, but is shot and hit with a grenade in process, resulting in the loss of both of her arms. Gilbert tells Violet to leave without him and finally tells her that he loves her, but she doesn't understand his words. Defeated, the enemy army bombs their own headquarters, and Gilbert sacrifices his life to push Violet to safety. In the present, Violet returns to the battle site to search for Gilbert. Hodgins then arrives and tells her that Gilbert had entrusted her care to him in case anything happened him. Violet returns to the post office with Hodgins, but refuses to do any more ghostwriting work, worrying her coworkers. In her grief, Violet attempts to commit suicide but cannot go through with it. After helping Benedict deliver letters and reading a letter sent to her by Erica and Iris, Violet comes to realize that the act of receiving a letter can bring someone joy. She returns to work, starting with ghostwriting a letter for Spencer, Luculia's brother. Violet returns to the post office and asks Hodgins if it is really okay for a person like her to live on. Hodgins responds that what she had done in the war can never be undone, but that also applies to all of the good deeds she has done as an Auto Memory Doll.
Episode 10: Violet arrives at a mansion where a young girl named Anne lives with her wealthy, but sickly, mother. Anne's mother has hired Violet for seven days to write letters, but Anne is not told what the letters are about or who they are for. In addition, Anne is both mistrustful and fascinated by Violet, as she mistakenly believes her to be an actual living doll due to her prosthetic arms. Over the next week Anne comes to accept Violet but cannot accept being separated from her mother while the letters are written. After an angry outburst by Anne, Violet manages to calm Anne down and convince her not to blame herself for her mother's illness. The letters written, Violet leaves and eventually the mother dies. Afterwards, Anne begins receiving the letters from her mother written by Violet and eventually grows up to start a family of her own. Back at the post office, Violet reveals to her co-workers that the letters would be delivered to Anne on her birthdays for the next fifty years and is overcome with emotion at the thought of Anne having to live alone after her mother's death.
Episode 11: The CH Postal Company receives a request for a doll from the neighboring country of Ctrigal, however the country is in a state of civil war between the warmongers and moderates. The request is from a soldier fighting on the front lines, but due to the danger Hodgins refuses the request. Violet overhears and travels to Ctrigal to find the client, Aidan Field. Aidan is fighting for the moderate faction, but his squad is annihilated by the enemy and he is gravely wounded. Violet arrives by parachute and rescues him. Believing that he is mortally wounded, Aidan has Violet write farewell letters to his parents and his childhood friend Maria confessing his love to her. With the letters complete, Violet comforts Aidan in his final moments as he pictures himself reuniting with Maria. Violet delivers the letters to Aidan's parents and Maria. Despite being saddened by Aidan's death, they thank Violet for delivering his final letters to them. Violet then breaks down in tears, apologizing for being unable to protect Aidan.
Episode 12: Dietfried is ordered to protect a special envoy who will be traveling to a conference to sign a peace treaty formally ending the war. Meanwhile, a rebel anti-peace faction led by General Merkulov plans to ambush the envoy in order to stall the peace talks. Cattleya and Benedict accompany the envoy as they board a train to travel to the city of Distery. Meanwhile, Violet, returning from Ctrigal, notices a number of fires near the railroad. Upon learning that Cattleya is on the train, Violet decides to accompany them for protection. However, the anti-peace rebels have already infiltrated the train, and after it leaves the station they stage an attack. Violet attempts to fight back, but is eventually restrained due to her refusal to kill anybody. Dietfried rescues Violet, although he blames her for Gilbert's death and tells her that she has no reason to live. Violet counters that Gilbert's final order was for her to live on, and that she regrets not being able to protect Gilbert. At that moment, a rebel fires a rifle grenade at Dietfried, but Violet deflects the grenade with her prosthetic arms.
Episode 13: Violet continues to protect Dietfried, losing one of her arms in the process. However, the train approaches a bridge, and General Merkulov reveals that the bridge has been rigged to explode as a backup plan before leaping off the train. Violet and Benedict go to remove the bombs, and Violet sacrifices her other arm in the process. With the envoy safe, the party continues on to the peace talks, where Leidenschaftlich and Gadariki officially sign a peace treaty to end the war. Upon returning to Leiden, a popular event called the Air Show, where planes are loaded with letters that are released in the sky to rain down all over the country, is being revived due to the peace. While Violet's coworkers are writing letters to submit, Cattleya suggests she write a letter to Gilbert. However, Violet cannot find the words to say. She is then invited by Dietfried to visit his and Gilbert's mother. She assures Violet that she does not blame her for Gilbert's death, and that he lives on inside her heart, even if the memories are painful. As Violet leaves, Dietfried notes that she's become fully independent thanks to Gilbert's teachings. Now inspired, Violet writes a letter to Gilbert for the Air Show. In it, she tells Gilbert how she's learned so much as an Auto Memory Doll, and that she plans to keep on living in the hopes that she'll meet him again so she can tell him that she now understands the words "I love you." a little more. Through this, she finally comes to terms with Gilbert's loss. The next day, Violet receives a new ghostwriting request and returns to work, introducing herself to her client.
OVA: Between the events of episodes 4 and 5, Violet is hired by Irma, a famous opera singer, to write a letter for her for a soldier missing in action. However, Irma's requests for the letter are both vague and complex, making it difficult for Violet to write a letter that can satisfy her despite numerous rewrites. Irma's conductor, Ardu, then reveals that Irma is in fact trying to use Violet to write the lyrics of the song she plans to use in her next opera play. Determined to complete the job, Violet decides to follow Irma to better understand her heart. Irma reveals to Violet that her boyfriend Fugo, Ardu's son, left to fight in the war but never returned. Though she understands Irma a little better, Violet is still not confident that she can write the letter she wants. Roland then takes Violet to an old military warehouse containing letters that were unable to be sent to soldiers that were missing or killed in action. Violet gains inspiration from reading these letters and writes a new one that moves both Irma and Ardu. Irma uses the letter as the basis for her song in her new opera play. As Irma sings, the song helps both her and Ardu move on from the loss of Fugo. The song is a great success, earning praise from the audience, and Ardu is confident that Violet will come to understand "love".