how do unlock the warp doors in deltarune chapter 5
You unlock the warp doors in Deltarune Chapter 5 after reaching the point where they become available in the late-game route, then you can use them to revisit missed areas and collect remaining Pink Coins. The key step for the pink secret door is to buy the Mystery Key from the Cliffside/Cliffs shop after collecting 10 Pink Coins , then return through the warp door and open it.
What to do
- Progress the chapter until the warp doors activate.
- Gather at least 10 Pink Coins.
- Buy the Mystery Key from the shop in the Cliffs/Cliffside area.
- Go back through the warp door and use the key on the pink locked door.
Useful detail
The warp doors are mainly there to help you backtrack for missed collectibles, and one guide notes they become useful once you can fast-travel back to earlier spots in the chapter.
Context
If you meant the pink secret door rather than the warp door itself, the answer is the Mystery Key plus 10 Pink Coins.
TL;DR: reach the warp-door phase, collect 10 Pink Coins, buy the Mystery Key, then return and open the pink door.