Answer
The answer is as follows. 
Katrielle and the Millionaires' Conspiracy walkthrough
Puzzle Location: Entrance hall (The left iron of the blue door)
This is a mysterious magical world.
There are three people standing in front of a gate, a bird handler, a snake charmer and a butterfly keeper.
The following conversation takes place:
A: 'I am not the gatekeeper.'
B: 'Neither am I.'
C: 'I'm the gatekeeper!'
One of the speakers appears to be the gatekeeper, but which one?
Slide the circle to move it over who you think is the gatekeeper.
Everything said in the conversation is true.
C was telling the truth.
Look carefully at the appearance of their conversation.
Pay attention to the speech bubbles.
Where is the speech bubble in question coming from?
In this mysterious magical world, humans are not the only ones who can talk.
The answer is as follows.