Kishin Houkou Demonbane [Kadokawa the Best] Japan

Demonbane is a series by Nitroplus with mecha and Cthulhu Mythos elements. Beginning as an eroge visual novel for the PC, it was ported into a PlayStation 2 non-eroge remake, and spawned a sequel visual novel, a prequel novel, an anime television adaptation and a conversion to manga. An English version of the original Demonbane PC game has been released by JAST USA. The anime is streamed with English subtitles by CrunchyRoll.