There are many sections which only one person can get to while the other must be in there own characters section to solve it. Get your friend to download the split fiction friend's pass on the playstation store, microsoft. The answer is no, both players do not need to buy split fiction to play together
Buy Split Fiction - Electronic Arts
Thanks to the friend’s pass, only one person needs to buy the full game
This means two friends can play the entire game without needing to buy two copies.
One person must own a copy of split fiction to utilize the game's friend's pass system
