I guess I'm disappointed because most publishers tend to split this into a new entry or series. For example, Dragon Ball (anime) was supposed to be about Goku, while Dragon Ball Z was supposed to be about Gohan. One of the names they even kicked around for DBZ was Dragon Ball: Gohans Adventure. While the manga changed the protagonist, the anime changed it into two separate series. The Gameboy Advance games Golden Sun did the same thing as well. The novel Brave New World switches protagonist halfway through.
Anyway, I'm looking for any sort of series like this. Wether its split into two parts or not. What would you guy recommend?