Yellow and Blue are one of the most unusual boss fights in DELTARUNE, and not just because of their names. This duo encounter in Chapter 5 plays out as a courtroom drama rather than a straight damage race. You take on the role of judge, work through four separate criminal cases, and point the finger at the right suspect each time. Get it wrong and you're stuck replaying attacks until you figure it out.
The good news is that every case has a single correct answer, and the evidence you need is either already in your inventory or available from Blue directly. This guide covers all four trial solutions plus the attack patterns you'll need to survive between rounds.
How does the Yellow and Blue boss fight work?
This fight does not end by dealing damage. Instead, you resolve it by running Kris' Justice ACT on Yellow to trigger a trial. Each trial presents a crime, a list of suspects, and a set of evidence items. Pick the right suspect and the matching evidence, and the case closes. Four cases closed means the fight ends.
Before you can start a trial, you need two things:
- Enough TP to initiate the Justice ACT. Use Susie and Ralsei's ACTs to build TP if you're running low.
- Sufficient evidence. If you're missing any, use Kris' ACT on Blue and select the Evidence option. Blue will hand over whatever you're missing so you can proceed.
The suspects across all four cases are Aqua, Seth, Green, Yellow, and Blue. Each case implicates a different one.
Deltarune Chapter 5 Guide: How to Beat Yellow and Blue
All four trial answers
Case 1: The Floradinn was crushed flat
The victim here is a Floradinn who reports being crushed flat without permission. Five suspects are presented.
- Culprit: Seth
- Evidence: PerpBook
Seth always carries the PerpBook, and it contains flower petals that tie her directly to the scene. Accuse Seth and she will confess, closing the case.
Deltarune Chapter 5 Guide: How to Beat Yellow and Blue
Case 2: Yellow's shirt was vandalized and turned black
Yellow steps forward as the victim this time. His favorite yellow shirt has been half-blackened by someone.
- Culprit: Green
- Evidence: YellowShred (the tattered piece of the yellow shirt)
The torn fabric directly links Green to the vandalism. Accuse Green and she admits to the crime.
Case 3: Green's handkerchief was stolen
Green is now the victim. Her handkerchief has gone missing, and before you can start this trial you'll need to request evidence from Blue first.
- Culprit: Aqua
- Evidence: RedSplatter
Aqua took the handkerchief and tried to alter its appearance, which explains the red splatter. Accuse Aqua to close the case.
Case 4: Yellow's secret special petals have gone missing
Yellow is the victim again. His secret special petals have disappeared, and this final case points at the most surprising suspect.
- Culprit: Blue
- Evidence: String (referred to as Blue String in some parts of the fight)
Yellow will react with anger when you accuse Blue, but Blue will confess regardless. This triggers a cutscene where Yellow attempts to punish himself, only to find that the bullets in his revolver have been replaced with blue flowers. Yellow decides the fight is over, and the encounter ends.
Deltarune Chapter 5 Guide: How to Beat Yellow and Blue
How do you survive the attacks between trials?
Between each trial, Yellow and Blue launch attacks that you need to dodge. There are three distinct patterns to watch for.
Flower petal waves: The duo fires flower petals in wave formations. Move in the same direction as the wave to avoid taking hits. Fighting against the wave's direction is how most players get caught out.
Scattered petal burst: Blue launches flowers into your container, then Yellow shoots them and the petals scatter. The key here is positioning yourself between two flowers at all times. Petals move slowly immediately after being fired before accelerating a second later, so staying close to the slow-moving petals gives you the safest window to dodge.
Dancer attack: Blue sends mini dancers into the container. They spin and jump in an alternating pattern. Track the alternation and stand on top of the stationary dancers to avoid damage.
Deltarune Chapter 5 Guide: How to Beat Yellow and Blue
Tips for managing TP and evidence
- Susie and Ralsei are your TP generators. Their ACTs build meter faster than sitting through attacks, so use them proactively before triggering each new trial.
- Blue is your fallback for evidence. Any time you're missing an item, the Evidence ACT on Blue covers the gap. There's no penalty for using it, so don't hesitate.
- You do not need to damage either boss to progress. Spending actions on attacks is a waste of turns that could go toward building TP.
- The fight is entirely pacifist-compatible. All four cases resolve through ACTs and accusations, with no combat damage required.
For a full breakdown of everything surrounding this encounter, the Deltarune Chapter 5 complete walkthrough covers the honey toast opening, castle puzzles, the festival, and the Dark World flower shop sections that lead up to Yellow and Blue.
DELTARUNE sits firmly in the RPG games category where creative boss design like this thrives, and Yellow and Blue are a strong example of Toby Fox building encounters around narrative rather than stats. For more guides covering the rest of the game, the full DELTARUNE guides collection has you covered.