Moonstone is a Japanese visual novel studio known for creating adult-oriented bishōjo games. The founding members of Moonstone had once been members of Circus, a similar visual novel studio. After the establishment of Moonstone, a collaboration project between Moonstone and Circus was set up for Circus' game Suika AS+, and then another collaboration project between the two companies was set up for Moonstone's game Gift. On 2009 Moonstone established the sub-brand Moonstone Cherry, which focuses on nukige titles.
Source: Wikipedia, "[en.wikipedia.org/wiki/Moonstone_%28company%29 Moonstone (company)]", available under the CC-BY-SA License.