The reader, at a young age, summoned the Heroic Spirit of King Arthur, the version mankind told stories of and was believed to be, a Man who was a great king and respected everyone, even his Enemys. The reader is attacked by a Stray Devil, and is close to death, so Arthur gives the reader his Spirit Origin, saving his life by turning him into a Demi-Servant, but he was still a master, at this time the reader is 12. A year later, the reader Summons a new spirit, Mash Kyrielight, a Fellow Demi-Servant. The reader Discovers the darker side of the Church, and sees to it to purge this darker side of it, eventually finding... Clarent!

The reader can communicate still with Arthur, similar to a sacred gear spirit can speak to its host.