Here you can find links to all of the walkthroughs for Code: Realize ~Guardian of Rebirth~.
Lupin’s route is the only one that’s locked at the start of the game. There’s no real risk of reading spoilers by picking your favourite character first as the initial four routes are quite standalone. Lupin’s route ties everything together and unlocks after you complete the other four.
My recommended play order is as follows:
Impey → Van Helsing → Fran → Saint-Germain → Lupin
After your first playthrough, you can start a different route via the Path of Genesis and select whose route you would like to start from Chapter 8. However, doing this will make you miss some Glossary entries (if I remember correctly, Impey’s route is the only exception to this).
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