The length of the side story in Fire Emblem Three Houses can vary. It depends on how much you explore and complete the various quests and events.
The length of the side story in Fire Emblem Three Houses is quite flexible. It depends on your playstyle and how thorough you are. Some players finish it relatively quickly, while others spend a significant amount of time uncovering all the hidden elements.
The side story of Fire Emblem Three Houses doesn't have a fixed duration. It could take a few hours if you focus mainly on the main objectives, but if you want to fully immerse yourself and complete all the optional content, it might take much longer.