Egoist is a Japanese pop music duo consisting of songwriter Ryo of Supercell and vocalist Chelly. Originally formed to produce theme music for the 2011 anime television series Guilty Crown, the group continued creating other songs after the end of the series including themes for other anime television series including Psycho-Pass and Kabaneri of the Iron Fortress. Egoist's debut album Extra terrestrial Biological Entities was released in September 2012.

Source: Wikipedia (https://en.wikipedia.org/wiki/Egoist_(band))