Guide
Deltarune: How to Unlock the Secret Boss in Chapter 5
Discover how to unlock the Secret Boss in Chapter 5, the latest chapter of Deltarune, including how to get Mysterious Key.
With the release of Chapter 5: Festival Day, players are once again diving into the Dark World to explore new secrets. The Flower Kingdom, the main Dark World place of Chapter 5, holds a lot of new secrets. One of the key secrets that players usually hunt is the secret boss. Chapter 5: Festival Day includes a secret boss, and it is pretty well hidden. In this guide, we will walk you through how to unlock the secret boss in Chapter 5 of Deltarune.
How to Unlock the Secret Boss in Chapter 5 – Deltarune

The Secret Boss in Chapter 5 of Deltarune is Pink, mainly known as Mad Mew Mew. Players can find Mad Mew Mew towards the end of the chapter in a secret area. It is a locked Pink Door at the castle that players can reach by dropping down from the top of the castle. To unlock the Pink Door, the players must use the Mysterious Key, which they can purchase from the Shop in the Cliffs area. However, the Mysterious Key costs 10 Pink Coins.
How to Get Pink Coins in Chapter 5 – Deltarune
The Pink Coins are the new special currency, exclusive to Chapter 5. The Pink Coins are obtained from the pink chests and bells scattered throughout the 2D platforming area. Accessing these 2D areas requires a key item, called Petal Feather. Players must defeat the Aqua boss to get their hands on the Petal Feather. There are 19 Pink Coins in total that players can find in the Garden, Cliffs, and Castle areas.
| Area Name | Location |
|---|---|
| Garden | On top of the temple, from where you get the Petal Feather. |
| Garden | At the End of Garden magic door. |
| Garden | Drop by Tropical Starwalker Bird. |
| Garden | On top of the lake. |
| Cliffs | Left of Ralsei’s vine. |
| Cliffs | Above the scarecrow enemy. |
| Cliffs | In the bottom cave. |
| Cliffs | The next room to Aqua and Seth’s bullet hell room. |
| Castle (East) | Below the Terakota Statues room. |
| Castle (East) | Above the Terakota Statues room. |
| Castle (East) | On top of the mysterious puzzle. |
| Castle (East) | Break the Pink Lantern. |
| Castle (East) | Fox Room. |
| Castle (East) | On top of the mysterious puzzle. |
| Castle (East) | Behind the bar. |
| Castle (West) | Platforming challenge in Blue’s Room. |
| Castle (West) | Get past the Shuriken Challenge. |
| Castle (Top) | On top of the castle, beside the yellow flowers. |
| Castle (Top) | The Pink Door. |
After acquiring any 10 Pink Coins, head to the Shop in the Cliffs area. Purchase the Mysterious Key, and then make your way to the Pink Door.
How to Reach and Unlock the Pink Door in Chapter 5

To reach the Pink Door, you must first head to the very top of the castle area. From here, go to the left side until you find a pit in the path. Drop down to the very bottom of the pit to reach the Pink Door.
Interact with the Pink Door and use the Mysterious Key to unlock the Pink Door. Head inside and go through the initial dialogues to initiate the secret boss fight with Pink (Mad Mew Mew).
