Here is a guide on how to find all keys in Kitten Burst.
Nullspace Castle

Under the bridge

On top of the server
On top of the server
Inside the jug
Under the bench
In the abandoned house
In the abandoned house
Under the circuit
The Eternal September

On the roof

In the ceiling fans
Over the BasilRips hyperlink
Inside the decorative orb
Behind Orator’s table
In the mast support
Under the cockpit
Anemoi

On the roof

In the building
On the windmill
Between the boxes
Next to the snowflake
On the canopy

In the upper orb

Behind the sign
Scratch

In the upper nook

In the large lower nook
Under the spawn
FireFray

Above the blue goal

Inside the cage
Inside the crate
Surf Haven

Above the entrance

Underneath the outermost surf
The World’s Longest Site

Inside the ticket booth
Congratulations, you won!
DigiGal

On top of the tree
Behind the large pillar
In the gift shop
Underneath the exhibits
The Arbormyth

Inside the treedome
Next to the tree
Inside the leaves (it’s clipping through a wall lol)
bounce2me dance

Here’s the entrance in case you haven’t found it yet
The key is in the bottom-right corner
Club BasilRips

On the bar
Next to the satellite
Inside the Pando Pillar
On the stack of wares
Planet eClips
The Lost Loch

In the tavern chimney
In the well
In the house
At the top of the library
Next to the merchant
Under the Archdruid
In the windmill gears
In the ninja course