Even though I'm closed in me, I love you.
I am entirely in you, even though I'm closed.
When I'm onto something, it's still me.
If it's you one by one, we're together.
No matter how I multiply, it's still me.
No matter how you multiply, it's still you.
If I am broken, I still love you.
So that we could find a point to fix me back.
What are we?
I am after a common word. You are after a mathematician.
The line of numbers is you, and also a broken me.