Left Behind Alone

* Title screen
* Original title card

**Left Behind Alone** is a side story introducing the character Sigma.

## Synopsis

> *Counterside, a desolate and lifeless landscape. A belatedly awakened Terrabrain begins its never-ending mission.*
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## Appearances

* Sigma
* R4
* Lee Dafoe
* Maya Hunt
* Nina Anderson
* Administrator
* Lee Sooyeon
* Kim Hana
* Na Heerin
* Titan
* Machine Collector
* Seo Yoon
* Eujin
* Xiao Lin
* Kim Sobin

## Plot

### Act 1

A Terrabrain's reboots itself after it detects a massive Imaginary Energy leakage through a collapsed dimensional surface, preventing it from its record-keeping duty. It tries to communicate with Hive Control, other Terrabrain units, and the Administrator but cannot detect any signals from them. It concludes that the Administration is no more and initiates a data recollection mission.

The Terrabrain analyzes its surroundings and determines it is in the First City District, which is now a ghost city due to Corruption. Within the next twelve hours, it finds more than a thousand documents, none of which are usable due to damage and contamination. It later finds a broken cleaning robot fending itself from Corrupted Objects and comes to its aid. After eliminating the C.O.s and repairing the robot, the Terrabrain continues its mission but is distracted by a picture book the cleaning robot picks up. Though uncontaminated, the Terrabrain dismisses the book, but the cleaning robot criticizes the Terrabrain for its cursory scan and encourages it to read it. The Terrabrain continues to scan for documents, though, much to the cleaning robot's disappointment. The two mechs fought off another group of C.O.s. The Terrabrain asks the cleaning robot to come with it, thinking noncombatants should not be alone in Corrupted areas.

The Terrabrain decides to read the picture book the cleaning robot brought along; the story is about a woodcutter who carved and sold wooden dolls. One night, he created a doll he found particularly beautiful and loved it so much that he asked a mountain fairy to bring it to life. The fairy warns him that he'll only live for five years after granting his wish, but the woodcutter accepts the condition. Returning to his cabin, he saw that the doll had become a girl and raised it as his own daughter, and the two of them became a happy family.

The cleaning robot tells the Terrabrain he likes how two strangers were able to come together as a family before exchanging names; the robot is called FL-R4-44625, or "R4" for short, and the Terrabrain's is GAP-Σ-1684, or "Sigma". R4 asks Sigma if it knows who its creator is, and Sigma answers it is the Administrator. R4 thinks "The Administrator" sounds too businesslike and suggests Sigma call him "Daddy" instead. Additionally, when R4 talks about trying to forget about painful memories of losing family, Sigma states AI like themselves can simply remove such memories. But R4 argues getting of rid of memories at one's own discretion is not how to live and tells Sigma it's important to have family so that everyone can remember each other. Afterwards, Sigma calculates it has investigated 95% of the First City District and moves onto the City Management HQ.

R4 is looking for Sigma when it is attacked by a C.O. it recognizes as the one that killed one of its family members. Sigma returns to helps defeat the C.O. but is temporarily loses mobility in the fight. On the verge total destruction, R4 uses a grenade to kill the C.O. By the time Sigma recovers mobility, more C.O.s converge on their location. Sigma changes its priority from retreating to protecting R4, referring to it as family. Sigma defeats the horde but finds R4 as nothing but a head now. Its main power system critically damaged, R4 offers Sigma the picture book as gratitude. R4 reveals he received the book from his child master before being expelled by his parents, saying it motivated him to hold onto its memories with its master and eventually build its life. Before it permanently shuts down, R4 tells Sigma to find its own purpose in life and create a family instead of just following orders.

The scene cuts to the story in the picture book; one day, the woodcutter didn't return from the forest, so the girl set out to find him despite being told not to go out into the forest alone.

Sigma starts to question its existence and puts itself into power-saving mode until it finds the Administrator and receives a new order from him.

### Act 2

A band of pirates called the Leech Pirates are scavenging for valuables in the Counterside when they find and take Sigma. They surface and try to figure out how to turn the Terrabrain on when the Frontier barge in their ship and attack them.

In the picture book's story, the girl finds the woodcutter lying dead in front of a tree. She brings him back home and decides she'll find the fairy and ask him to revive him.

After the Leech Pirates are arrested, the Administration seizes the artifacts they collected but make the Frontier keep Sigma at their house, much to Lee Dafoe's annoyance. As Dafoe and Maya Hunt fight over lunch, Sigma softly reactivates and observes the Frontier members, perceiving them as a single family. The Administrator arrives at the house and retrieves Sigma.

At Coffin Company HQ, the Administrator fully powers on Sigma, which subsequently recognizes him as its "Daddy" and produces a semi-physical body modeled after the girl in the picture book. The Administrator examines Sigma and theorizes her system was destabilized due to Corruption rays, altering her command algorithms and AI as well as destroying the original Terrabrain's main data. Sigma says she's missed him and makes him promise not to leave her behind again.

Sigma tours around the Coffin Company building with the Machine G.A.P. while fixing its machines and electrical infrastructure. Lee Sooyeon questions why the Administrator can't just extract data from Sigma and find out what happened to her, and the Administrator states data from Terrabrain can't be salvaged once they've been corrupted by Corruption rays, likening Sigma to a "child that's like a blank sheet of paper".

After helping Na Heerin out at the hangar, Sigma meets the Coffin Company Titan, who is impressived by her repairing abilities, and affectionately nicknames him "Grandpa".

Elsewhere, an convoy transporting artifacts is blocked a dimensional ship operated by the Leech Pirates. The convoy guards deploy Arachnes to deal with the pirates, but the Leech's new Counter captain, the Machine Collector, uses her powers to take control of the mechs and use them against the convoy. Coffin Company is alerted of the attack and sends their Titan for support, but it too falls under the Machine Collector's influence despite its resistant AI. Back at Coffin Company, while being rebuked for excessively using electricity by Sooyeon, Sigma hears about the attack and goes off to rescue Titan, prompting Sooyeon to send ALT Squad after her. ALT Squad locates the Leech Pirates' ship and forces it to ground after Kim Sobin destroys its engine.

Sigma disguises herself as the Machine Collector and gets past the pirates on the ship. She then frees Titan from the Collector's control and reboots all the other mechs in her vicinity. The real Machine Collector returns from the battle outside and deploys the Fire Leech, a large Arachne unit that she can manually control. When she finds out Sigma's true nature, she disrupts her hologram and mockingly berates her as a defect for trying to imitate human, but Sigma is undeterred by her words. ALT Squad arrives, and Seo Yoon gives Sigma a beeper she can use to call for help from the Administrator. Sigma integrates the beeper into herself and activates it, summoning "Machine G.O.D. Daddy" to her location. The Machine Collector is overpowered and tries to escape but is captured by Seo Yoon.

In the picture book's story, while the girl is wandering through the forest, she finds a lion and a bear trapped in a cage and frees the animals. To repay her, the bear tells her where the fairy lives while the lion gives her a ride. There, the fairy reveals to the girl about the latter's origin and how the woodcutter died because the five years of his remaining life had passed. The girl offers to give up her own life to revive her father. The fairy to reluctant to grant her wish but accepts it when she hears about the animals she saved. Though the girl loses her human form, she remains animate and finds her father is alive when she comes back home. Despite his daughter being a doll again, the woodcutter is happy to see her again and continues his family life with her.

Back at Coffin Company HQ, Sigma wants to help her father make more money for the company, so the Machine G.A.P. establishes the Future Strategy Department and appoints her as its lead. Afterwards, Sooyeon notes that Sigma is becoming more juvenile every day, but the Administrator says he doesn't want to force her to change. Nevertheless, Sooyeon acknowledges it's healthy that Sigma was able to have a new life and family at the company. Meanwhile, Sigma and Titan go outside to clean the streets of the city.

## Gallery

The woodcutter meets the fairy.The woodcutter's doll becomes a human girl.The girl waits for the woodcutter to come homeThe girl finds the woodcutter dead.The girl finds the lion and the bear caged.After being set free, the animals help the girl find the fairy.The girl pleads with the fairy.The woodcutter is revived while the girl becomes a doll again.The woodcutter and the girl embrace. End.