![cover](https://s4.anilist.co/file/anilistcdn/media/anime/cover/medium/1157.jpg)
Ai and Yu, after reading their parent's research and after their parents' disappearance, they decided to go on search for them. They ride a strange train to the Inner World in search of their parents and meets up with Lisa in the train and together they begin their journey within the Inner World.
(Source: ANN)
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