Sirius is the leader of a dark group called Avelicia, a group that takes people's energy stones and uses them for evil things. Sirius is actually the reincarnation of the Prince of the Stars in the good past, but his good nature has turned evil since his wife, Vivilia, died and her heart was taken to be used as an energy stone, which is what makes Sirius hold a grudge that extends to his second life. It wasn't just Sirius who reincarnated, in fact Vivilia also reincarnated and changed her name to Luna and joined the special forces that would eliminate Avelicia's group. and during the fight Sirius met Luna