It's cold because of the office air conditioning, so I'm looking for a single-layer jacket that's good to wear indoors.

I picked two safari jackets lightly made as a single layer without lining. Made of 100% nylon material, they are great for throwing on comfortably indoors, and you can adjust the fit with the cuff buttons and the drawstring inside the waist. You can check them out in two colors: black and olive.

Here is the single-layer safari jacket in black that you mentioned. It has no lining, making it great to lightly slip on indoors where the air conditioning is running, and you can adjust the silhouette using the inner waist drawstring and the cuff buttons. It is made from Japanese nylon fabric with a water-repellent finish.

There are two areas to adjust by hand: the two buttons attached to the cuffs and the drawstring inside the waist.