Let me walk you through unlocking those alternate storylines - they're actually quite interesting because they let you change history's course (which explains those "fate altered" messages you'll see).

For liu bei's path, you'll want to make your way through until changban in chapter 5. Now here's something crucial - instead of running away like history says, wait for cao cao to show up in the northern area and defeat him there (this changes the entire timeline of the three kingdoms). A lot of players miss this because they rush through too quickly.

If you're following cao cao's story, there are two key officers you need to keep alive, because they're vital to changing wei's destiny. Save dian wei during the wan castle escape by capturing bases quickly, then protect guo jia at mt. Bailang. Here's the important part - make sure guo jia is your companion at chibi and take down huang gai before he can start that famous fire attack (having guo jia with you actually unlocks special dialogue that explains the strategy).

For the sun family storyline, there's an interesting twist in chapter 3 - you'll need to find and defeat a phantom version of zhang jiao to save sun jian. Later, when trying to save sun ce, look for a hidden path to the southwest (this represents the sun family finding their own way forward rather than following their historical fate).

Maybe interesting - playing on historian difficulty makes these alternative paths much more manageable, especially wei's route which can be pretty challenging otherwise. Remember, these endings aren't just different for the sake of being different - they represent what might have happened if key historical figures had survived their famous deaths.