Riku is the 12th Prince of the Holy Britannian Empire and the son of the 98th Emperor of Britannia, Charles zi Britannia. He is the leader of the Black Knights which makes him the real identity of Zero. Sora is the 13th prince of the Holy Britannian Empire and the 12th Prince Riku ki Britannia's blind and crippled younger brother.

Self-explanatory.

As a young summoning apprentice, Fulein K. Lester and his fairy-like companion Macaron are studying the principles of calling upon magical beasts into the physical world. However, their exploits are cut short when a significant number of monsters and other beasts begin to appear within their world, threatening the stability of the usually peaceful nation.

The story begins when what appears to be a shooting star lands in the mountains. The narrator describes the player, referred to in second person, finding a pair of twin babies in the light and becoming their adoptive parent. By default, the boy is named Dio, and the girl is named Mell.