Looking for 91Days OST as well. :33
http://vgmdb.net/album/59943

Samples are up for it as well
https://www.amazon.co.jp/%E3%80%8C91Days%E3%80%8D%E3%82%AA%E3%83%AA%E3%82%B 8%E3%83%8A%E3%83%AB%E3%83%BB%E3%82%B5%E3%82%A6%E3% 83%B3%E3%83%89%E3%83%88%E3%83%A9%E3%83%83%E3%82%AF-%E6%B5%B7%E7%94%B0-%E5%BA%84%E5%90%BE/dp/B01HLDYRXY/ref=sr_1_4?ie=UTF8&qid=1474171743&sr=8-4&keywords=91+Days

link here (http://hikarinoakariost.info/91-days-original-soundtrack/)