Long undergarment for kimono?

I found this at my parents' house.

I'm not sure what it's for, but it was with a hadajuban (undershirt), so I'm guessing it's a longer type of hadajuban. That's why I'm listing it.

It looks unused, so I believe it's in new condition.

I hope someone can use it.

#hadajuban (undershirt)