Honestly, I thought Rei was lying through his teeth when he said he knew Kou's mother. Kudos to the writers for writing such a compelling character. He came across as untrustworthy, working for the villainous Kai as his informant so his character came off as dubious at best. They shed more light upon the lore of this world in this episode. We now have the answers to where the jewels came from, and how they fit into the plan Fuse left behind for her descendants. A wild ride can't wait to see how they all answer the call!