Jubans & Haneri CollarsThis item is called a Juban. Jubans are decorative under-robes worn beneath a kimono and over the undergarments. Typically jubans are just slightly visible at the neckline, hem and sleeves when you move, so they were usually coordinated to the outer kimono. Jubans are also known as Naga-juban.
A haneri is a decorative collar sewn onto the lapel of a juban to protect the garment as well as accessorize to suit a different outer kimono pattern. Not all jubans have a haneri attached, many vintage jubans have long since lost their haneri. A haneri, if still present on a juban, is almost always lightly sewn on top of the under-collar with a basting, straight or whip stitch so it can be easily removed to be cleaned or replaced quickly with a different style. Most under-collars are made of either the same material as the juban or they are made with plain cotton muslin. Almost all haneri collars are not stitched along the bottom edge and often the under-collar is left sticking out from the bottom of the haneri. This is not a flaw and it is not damaged, it is intentional as that part of the haneri and under-collar would never be visible from underneath the kimono and meant to be removed quickly. In the modern day, haneri collars are rarely ever stitched on to the juban, they are now called "Easy Collars" and are quickly pinned in place and removed after each use for cleaning.