The Yellow and Blue boss fight in Deltarune Chapter 5 is unlike anything else in the game. You do not win by dealing damage. Instead, Yellow puts Kris and the party on trial every other turn, and you have to name the correct culprit and present the right evidence to close each case. Get it wrong and the duo just replays their last attack pattern until the next trial comes around. There are four cases total. Solve all four and the fight ends.
- This fight is a trial, not a standard battle. You win by solving four cases correctly.
- Use Kris’ Justice ACT on Yellow to start a trial. It costs 40% TP.
- Case 1: Floradinn crushed — Culprit: Seth, Evidence: PerpBook.
- Case 2: Yellow’s shirt vandalized — Culprit: Green, Evidence: YellowShred.
- Case 3: Green’s handkerchief stolen — Culprit: Aqua, Evidence: RedSplatter.
- Case 4: Yellow’s special petals missing — Culprit: Blue, Evidence: BlueString.
- If you are missing evidence, use the Evidence ACT on Blue before triggering Justice.
How the Yellow and Blue Boss Fight Works
Yellow and Blue are flower-themed characters living inside the Flower Castle in Chapter 5’s Dark World. They are not trying to destroy Kris. They want justice. Yellow acts as the prosecutor and keeps dragging the party into trials. Blue acts as a kind of court assistant who can supply missing evidence when needed.
The fight runs on a loop. On one turn you dodge attacks. On the next you trigger a trial using the Justice ACT. The Justice ACT costs 40% TP to use. You must have enough TP saved before you can open a case. If you try to start a trial without enough TP, the option simply will not appear.
Between trials, use Susie and Ralsei’s ACTs to build TP back up. Do not waste turns attacking. Dealing damage does not progress the fight at all. The only way to end the encounter is to clear all four cases.
If a party member goes down during an attack phase, use Blue’s Integrity ACT to revive all downed allies at the cost of TP. Ralsei’s healing magic also helps keep everyone healthy between phases.
How to Start a Trial
To open a trial, select ACT on your turn, then choose Kris, and select the Justice option targeting Yellow. Once the trial begins, Yellow reads out the crime. You then choose a suspect from the list, followed by the evidence that links them to it. Both the culprit and the evidence must be correct to close the case.
If you pick the wrong suspect or the wrong evidence, the case does not resolve. Yellow and Blue simply loop their previous attack pattern until the next trial turn. Nothing is permanently locked, but wrong answers waste time and cost you health.
Before triggering a trial, always check that you have the required evidence in your inventory. If you are missing an item, select ACT, then choose Kris, and use the Evidence ACT on Blue. This costs around 20% TP and Blue will hand over whatever evidence you are missing. Do not restart the fight just because one item is absent. The Evidence ACT is the built-in solution for exactly this problem.
All Four Case Answers — Culprits and Evidence
The cases always appear in the same fixed order. Here are the correct answers for every trial.
Case 1 — A Floradinn Was Crushed Flat
A Floradinn reports being crushed without permission. This is the first and simplest trial. It acts almost like a tutorial to teach you how the system works.
- Culprit: Seth
- Evidence: PerpBook
Seth carries the PerpBook everywhere, and it contains flower petals that tie her directly to the scene. Accuse Seth and present the PerpBook. She will confess and the case closes. Remember that accusing the right suspect alone is not enough. You must also present the matching evidence to complete each trial.
Case 2 — Yellow’s Favorite Shirt Was Vandalized
Yellow steps forward as the victim this time. His favorite yellow shirt has been defaced and turned jet black. This case is straightforward once you identify the clue.
- Culprit: Green
- Evidence: YellowShred
The torn piece of Yellow’s shirt is the key. Accuse Green and present the YellowShred to solve the case. After this trial the fight starts leaning harder on TP management. If you are running low, spend a turn building TP before triggering Case 3. Do not rush into the next trial without enough meter.
Case 3 — Green’s Handkerchief Was Stolen
Green reports that his handkerchief has gone missing. This is the case where most players get stuck because the required evidence may not already be in your inventory.
- Culprit: Aqua
- Evidence: RedSplatter
Aqua stole the handkerchief and used food coloring on it while trying to make red ribbons. The RedSplatter is the leftover evidence. Before triggering this trial, check that you have the RedSplatter. If it is missing, use the Evidence ACT on Blue first. Once you have it, accuse Aqua and present the RedSplatter to close the case.
Case 4 — Yellow’s Super Secret Special Petals Are Gone
Yellow returns as the victim one final time. His most prized possession, his secret special petals, have disappeared. This is the last trial and the most surprising answer.
- Culprit: Blue
- Evidence: BlueString
Blue stole the petals to make a bouquet combining both his and Yellow’s flowers. When you accuse Blue, Yellow gets angry and refuses to believe it. But Blue confesses on his own. Yellow, shocked and devastated, aims his revolver at himself — only to find that Blue had replaced the bullets with blue flowers. Yellow decides the fight is over and calls off the whole encounter. A cutscene plays and you are free to continue into the castle.
How to Survive the Attack Phases
Between each trial, Yellow and Blue launch attack patterns you need to dodge. The fight is much more focused on the trial answers than on difficult dodging, but knowing what to expect helps.
Flower Petal Waves
Blue forms a dotted line that turns into a flower, then fires bullet petals in wave formations. Weave between the open lanes as petals fire across the box. Small adjustments work better than large panic movements. Do not drag your soul all the way across the screen for a single petal.
Bloom and Fire Pattern
Flowers appear on screen before firing, then turn their petals into moving obstacles. The approach is the same as the petal wave pattern. Watch where flowers bloom, identify the open lanes, and move steadily rather than reactively.
Music Note and Petal Rain
Music notes scroll across the screen while petals rain from the top and bottom simultaneously. Slip between the wavy note lines and watch the falling petals from above. Focus on one threat at a time and reposition between waves.
Ballerina Jump Pattern
Tiny ballerinas cross the bottom of the box and jump in an every-other pattern. Find a gap between two ballerinas and sit there, then shift your position over the one that is about to jump. Anticipating the jump timing is more reliable than reacting to it.
Tips for the Whole Fight
- Never spend TP on attacks. Damage does nothing. Every turn spent attacking is a turn you could have used building TP for the Justice ACT.
- Use Susie and Ralsei’s ACTs to build TP. Their ACTs generate meter faster than taking hits. Use them proactively before each new trial.
- Check for missing evidence before triggering Justice. If RedSplatter is not in your inventory before Case 3, use the Evidence ACT on Blue first. Failing to do this means the Justice ACT will not proceed.
- Use Integrity if a party member falls. Blue’s Integrity ACT revives all downed allies. Save enough TP to use it if things go wrong.
- Do not panic about taking damage. The attack patterns are annoying but not the real challenge. The trial answers are the only wall that can stop you. Getting hit just makes the fight slightly longer.
What Happens After You Beat Yellow and Blue
After the fourth case resolves and Blue confesses, Yellow calls off the fight entirely. The cutscene ends with Blue presenting a bouquet made from both their special petals. Yellow leaves happy. As the party tries to slip away quietly, Blue notices and tells them not to gaslight him again.
From here the chapter continues deeper into the Flower Castle. Blue actually follows the party for a short while afterward and offers to show Susie which flowers would be best. The path forward opens and you continue chasing Flowery to reach Asgore.
For more help navigating this chapter, see our guides on how to power the Mysterious Structure in Deltarune Chapter 5, how to solve the Deltarune Chapter 5 mushroom block puzzle, the Ralsei four block switch puzzle, and how to get the Egg in Deltarune Chapter 5 before the chapter locks out.
Where to Play Deltarune
Deltarune Chapters 1 through 5 are available now on all major platforms.
