How to DC small black cable?

Dear Experts,

I have a 1996 Honda Accord. 5 speed.

I'm having some starting issues. I've been looking at removing the starter motor.

There is the big cable that connects to the positive post. That's easy enough.

But on another part of the starter motor, there is a thinner, black wire. The other end goes into a sleeve near the engine.

I've been looking at how can this smaller black wire can be disconnected (DC). But nothing seems obvious.

How do I disconnect this wire?

Thanks a lot!