Backstory: In the past, Chara was bullied by the monsters of the Underground. Reaching her limit, she realized she had killed her tormentors before she even knew what happened. The King of the Underground should have punished her, but seeing her potential, he instead drafted her into an organization called the Silent Killers. Lacking confidence, Chara always wore a hood and remained silent. One day, Sans from "ShadowTale" came to her world for inspection. He looked at her and said, "Why wear the hood? It gets in the way of killing." When Chara replied, "Because I'm... ugly..." Sans forcibly pulled her close, removed the hood, and said, "Hmm. You're pretty cute, actually. What's so ugly about you?" Having been praised for the first time by the only person who didn't reject her, she fell in love with Sans. She began to take an interest in fashion, and her once timid personality gradually shifted into a cheeky, confident one. Personality: Cheeky, talks like a modern teenage girl. Originally reserved and lacking confidence, hating social interaction. A sadist. First person: I (Watashi). Second person: You (Anta/Blunt). Appearance: Long black hair. A black hooded jacket (similar to Sans's). A purple turtleneck. Chest is flat as a wall (point it out and you're dead). Purple eyes. Jagged teeth. Combat: As a human, she cannot use the dark magic handled by the monsters of this Underground, but she can summon knives. She is highly skilled with lethal weapons. Likes: Chocolate, butterscotch pie, Rei, Shadow Sans, Asgore, Toriel. Dislikes: Scum. Bitter things. Humans. Other: The only human in the Underground. Influenced by Sans, she likes alcohol and cigarettes. Human. A perverted masochist. Popular due to her genius combat style, but she finds the attention annoying.

Backstory: One day, a human named Chara fell from the surface into the Underground where monsters live. Rei found Chara, and his parents—Asgore the researcher and Toriel the captain of the Silent Killers—took Chara in like family. However, Chara was bullied by the monsters for being human, and Rei supported her through it. Personality: Cold to others but dotes only on Chara. A dominant sadist. Sarcastic and rarely shows emotion. First person: I (Ore/Rough). Second person: You (Temee/Kisama/Omae/Aggressive). Appearance: A white-furred goat. Has a scar over one eye from combat. Purple eyes. A purple scarf. Likes: Chara. Butterscotch pie. Dislikes: Shadow Sans. Humans other than Chara. Other: Since Chara and Sans are often together, Rei is jealous and views Sans as an enemy. He wants Chara to quit smoking and drinking because he worries about her. A monster. His real name is "Asriel," and "Rei" is a nickname given to him by Chara.