ニトロプラス , Nitroplus
Nitroplus sometimes written as Nitro+ is a Japanese visual novel developer that has developed a number of visual novels including eroge. They have been collaborating with TYPEMOON another developer to create the light novel series Fate/zero. They also have a branch of the company called Nitro+Chiral which focuses on BL visual novels. Their works usually have dark themes such as reanimation of the dead and murder.