Fan Casting Stranger in a Familiar Land in Sort by Tropes

Known in real life as "Reverse Culture Shock" or "Re-entry Shock". A character returns home after a long absence and finds that they no longer fit in, either because their home has changed too much over time, because they themselves were changed by their experiences or both. In the second case, it can lead to a But Now I Must Go sentiment. In less extreme cases, the character may eventually settle down again with some effort.