Nitro Plus

Nitroplus Co., Ltd., previously stylized as nitro+, is a Japanese visual novel computer software company that has developed a number of visual novels, including eroge. They also have been collaborating with TYPE-MOON (another developer) to create the light novel series Fate/Zero. Their works usually have dark themes such as reanimation of the dead and murder. They also have a branch of the company called Nitro+Chiral, which focuses on Boys' Love visual novels. Super Sonico is the mascot of Nitroplus' annual music festival event, "Nitro Super Sonico", since 2006. Nitroplus has held their music festival every year since 2000.

Source: IGDB