From white hair to black hair, what is this?

I don't dye my hair

I just cut off the top part of my gray hair.

But the other day, after cutting my gray hair, I was looking at it

I noticed that black hair was growing back.

It was fascinating and surprising, and I was super happy to see it lol

So I thought about it...

I wonder if this is due to stress.

I'm not sure what it is.

That said, other hairstyles aren't like this either.

Anyway, I thought I should eat black sesame seeds more diligently lol

The circled part is the white hair.