The phrase "unique storyline" refers to a story or plot that is one-of-a-kind, different from others, and has not been seen before. It is original and stands out from the rest. Full definition
So you have a total of six campaigns to choose from each with unique storylines. (gamerstemple.com)
Because we know exactly what you have said and all this other stuff, we are able to react to those things and we are able to create unique storylines. (blogs.sega.com)
One of the very unique storyline and one of the beautiful indie films of the 2015 that needs wider recognition. (metacritic.com)