'Time is singular, once you traveled back in time, time reverts itself back to its form to the time you traveled to.
There is nothing called a paradox.
Your past becomes your future while your present becomes the past, and the future has been gone the time you traveled.
You existed both in your past, present, and future.
But you can't change the future, why? Because the future is already happening, everything you do in the past. The you in the past had already done.
In the end, it all goes to one single doing. As people would call it, fate.'
Chiyo-chan wrote on her notebook, the belief that time travel exist is ridiculous to her.
Why did she decide to wrote it? Her friend asked her "do you believe in time travel?"
She answered "I cant seem to decide yet", that answer made her friend frown,"what can you decide?" Her friend asked once more.
She got irritated that her friend kept asking her, so she answered again, "I don't know, stop questioning me."
That's where the flashback ends, and we got to the scene at the kindergarten where Chiyo-chan store back her notebook to her desk.
It's napping time, but she stil felt uneasy by the question.
By the time she's reaching to her desk, she touched something she didn't know, that thing was a box.
She took out the box, and thought, who the hell put it in here? Suddenly, the box glow bright and a text appeared.
'Do you believe in time travel?'
Chiyo-chan's eyes widened "Holy shi-" she stopped herself before saying a bad word.