Obito knows that he 's not the first choice.

He knows that with a clarity he doesn 't for most things, ever since young.

He 's not the first choice for someone to take a look into a brand new classroom and go

I want to be that kid 's friend.

He 's not the first choice for a teacher to look at their new students and go

I think that one has the most potential.

He knows that he 's not the first choice for a new team to look at and go

I know he has my back.

Obito knows, with more clarity than he does for most things, that he 's not anyone 's first choice.

But he had swore to be their last.

It wasn 't the 'last ' of being the worst.

Rather, it was 'last ' in the kind of it being final. Of it being the only choice you 'd need to make from therein onwards.