Chapter 1
Chapter 1, titled The Beginning starts with the player creating a vessel that is abruptly discarded. Instead, they inhabit a vessel who they cannot choose: Kris. They are a quiet human teenager who lives with their mother Toriel and goes to the local school in Hometown. After being assigned a tall reptilian student, Susie, as a partner for a school project, she threatens to eat their face. They are forced to team up and go to get chalk from the school supply closet.
Upon opening it, the duo inadvertently discover the Dark World inside. There, they meet Ralsei, a kind hearted Boss Monster-like Dark Prince, who reveals that the three of them are the heroes of the Prophecy, destined to restore balance to light and dark. During their adventure, they meet Lancer, a goofy bad guy determined to stop them from reaching his kingdom's Dark Fountain. Feeling undervalued, Susie leaves Kris and Ralsei for a time and teams up with Lancer.
Susie's friendship with Lancer helps her become more compassionate. The whole cast ends up uniting into a single team of four. In the end, Lancer helps the trio overthrow his cruel father, King. Afterward, Kris and Susie say their goodbyes to the Dark World, and, using the power of Kris's human SOUL, they seal the Eastern Fountain.
Kris and Susie return to their world together, appearing in a room filled with toys and board games, representing the Dark World and the characters they met. Kris and Susie agree to return to the Dark World the next day. Kris can leave the school and explore Hometown.
Kris goes to sleep after exploring the town. In the middle of the night, Kris shambles out of bed, seemingly fighting just to walk. They rip out their SOUL and throw it into a birdcage, where it becomes trapped. A knife materializes in Kris's hand, and they look at the camera with a menacing smile as their eye glows red. The screen then goes completely black for a few moments before the credits play.
Chapter 2
The second chapter, titled A Cyber's World, begins with Toriel calling out to Kris. She then discovers a knife and acts shocked. However, it is almost immediately revealed that this is because Kris ate all of the pie she had baked the day before.
Kris wakes up, goes to school and enters the Dark World again with Susie. They meet Ralsei and explore the Castle Town, which has been significantly expanded by the addition of NPCs from Chapter 1. Eventually, Susie mentions they have homework to do, prompting Ralsei to banish them from the Dark World until their homework is done.
They go to the Library, where they find another Dark World, the Cyber World, awaiting them, and jump into it, this time after Noelle and Berdly, two of their classmates. They hear talk about a Queen, who acts as the main antagonist for this chapter, and meet her soon after. She captures Noelle, while Berdly switches to her side voluntarily. Eventually, Kris splits up with the other party members and teams up with Noelle. In Kris's company, Noelle learns to be less fearful, accentuating one of the game's themes of personal development.
Later, after the entire party gets thrown into Queen's dungeon, Berdly learns to be less arrogant after failing to solve multiple puzzles, although he takes the lesson a bit too far. After fighting Queen in her normal form, the final boss fight begins with both parties fighting inside mechas, and then combat proceeds in the style of a Punch-Out!!-esque fighting game. Kris seals the Dark Fountain of this world, and the Lightners all return to the Light World.
After walking through town, Kris goes home and Toriel invites Susie to spend the night at her house. She sends the pair to wash their hands. When Kris goes to the bathroom, they rip out their SOUL again and escape through the window, leaving the player to listen to a chat between Toriel and Susie. Eventually, Kris returns to the bathroom and puts their SOUL back in their body.
After Susie and Kris fall asleep while watching TV, Toriel calls the police to inform them that she saw something outside the house and found her car tires slashed. After that, Toriel also falls asleep in the living room. Later, in the middle of the night, Kris wakes up, and, with their knife, creates a Dark Fountain that envelops the entire room in black mist. The last thing that can be seen is the static television screen and a ghoulish smile on it. Then, the screen goes completely black for a few moments before the credits play.
The Snowgrave Route in Chapter 2
The Snowgrave Route is a hidden route in Deltarune Chapter 2 that can be accessed by performing a series of specific actions. It leads to a secret area with unique enemies and dialogue, as well as a new boss battle.
To access the Snowgrave Route, players must complete several tasks:
- Enter the password "SURVEY_PROGRAM" on the computer in the classroom at the beginning of the game.
- Interact with the egg in the forest and choose to "Take it with you."
- During the battle with Spamton, use the "Defend" option instead of attacking him. This will cause him to offer you a deal. Choose to "Refuse" the deal.
- After the battle with Spamton, return to the forest and interact with the egg again. This time, choose to "Leave it."
Once these tasks have been completed, the Snowgrave Route will be accessible by interacting with a snow pile in the forest. Players who complete the Snowgrave Route will be rewarded with unique dialogue and an alternate ending.