Balconette bra
From wipipedia.org
A balconette bra is one where the cups do not cover the upper part of the breasts but are designed to push them upwards. This makes the breasts more prominent, and also means that the cups cannot be seen even if the wearer has a top with a low neckline that partly exposes the breasts.
See also
A fetish is defined as any inanimate object given unreasonable attention, or any part of the body not of a sexual nature that arouses erotic feelings.