Deltarune Chapter 5: Festival Day officially launched on June 24, 2026, continuing the story of Kris, Susie, and Ralsei as they venture into a brand-new Dark World known as the Flower Kingdom.
The chapter introduces new characters, enemies, puzzles, and secrets while expanding the mystery surrounding the Dark Worlds.
Players once again take control of Kris, accompanied by the fearless warrior Susie and the kind-hearted prince Ralsei.
Together, they’ll battle challenging enemies, solve environmental puzzles, explore hidden areas, and uncover the secrets buried within the Flower Kingdom.
Many locations reward careful observation and creative thinking, with optional paths leading to valuable items and hidden encounters.
In this guide, you’ll learn how to find the Secret Boss and use the Mystery Key in Deltarune Chapter 5, including all the requirements and a complete step-by-step walkthrough.
Deltarune Chapter 5 Secret Boss
To unlock the Secret Boss in Deltarune Chapter 5, you’ll need to complete a hidden questline involving Pink Coins and the Mystery Key.
Start by collecting all of the Pink Coins scattered throughout the chapter. Once you’ve gathered enough, visit the Cliff Shop and purchase the Mystery Key.
Step 1: Collect 10 Pink Coins
- Explore the map and collect 10 Pink Coins.
- One coin is located near the Secret Door.
Step 2: Buy the Mystery Key
- Go to the Cliffs Shop.
- Enter the shop and purchase the Mystery Key for 10 Pink Coins.
Step 3: Find the Secret Door
- Return to the main platforming area.
- Climb the platforms, then carefully drop into the hidden lower section.
- Head to the bottom to find the Pink Door.
Step 4: Unlock the Secret Boss
- Use the Mystery Key to open the Pink Door.
- Enter the room to challenge the Chapter 5 Secret Boss.
