Book Four: Duet
Childhood friends with opposing personalities, Mingi and Ryan, dream of becoming rock stars but find themselves on the Infinity Train. They explore the locomotive's inner puzzles — and their own relationship — in order to return home, together.
Episodes
1 The Twin Tapes Apr 15, 2021 
2 The Iceberg Car Apr 15, 2021 
3 The Old West Car Apr 15, 2021 
4 The Pig Baby Car Apr 15, 2021 
5 The Astro Queue Car Apr 15, 2021 
6 The Party Car Apr 15, 2021 
7 The Art Gallery Car Apr 15, 2021 
8 The Mega Maze Car Apr 15, 2021 
9 The Castle Car Apr 15, 2021 
10 The Train to Nowhere Apr 15, 2021