Rare creatures that inhabit the upper atmosphere. They are the source of "bottled lightning," a energy source more powerful than standard fiendfire.
(Viewer Sentiment). The sudden appearance of the Ryuu reinforces the idea that the world is returning to an imbalanced state where ancient "gods" or monsters are reclaiming the land. Hikari no Ou - Episode 3
Aboard the cargo train, Benio successfully advocates for Touko to remain on board. Rare creatures that inhabit the upper atmosphere
The episode follows two parallel storylines that highlight the different scales of conflict in this world: to her new village.
The caravan is tasked with delivering another "bride," Hotaru, to her new village.