Since Narcissu is a free distribution, I think it is all right if i uploaded the OST file here. I really like the Narcissu Music as it is relaxing and enjoyable. Do download it because Narcissu has one of the best soundtracks that I have heard from any visual novel.
A personal recommendation would be to take a look at the visual novel. It is free and does not take much space, so do check it out here