I found a sealed copy of this on eBay but can't seem to find out when or how it was ever released. The copyright on the back suggests 2015 and so does the timestamp on the CD matrix according to the "Rainbo CA" label on it and this page on Discogs:
https://www.discogs.com/label/100643-Rainbo-Records The CDs have 090115 (September 01 2015) on them so it has to be sometime after then.
The only other info I've found is this tweet from a developer about it.
https://twitter.com/ashuraou/status/674422106113900544 I've tried to reach out and see if that can help at all.
EDIT: Got a reply, it was a reward from their IndieGoGo campaign.