The phrase "main narrative" refers to the central or primary story or plot in a particular situation, book, movie, or event. It is the most important thread of the storytelling. Full definition
Are you hoping for a deeper main narrative and co-op play out of the next installment like me? (shortpause.com)
Truth be told the quality of both the writing and main narrative thread is all over the place, bouncing madly from genuinely beautifully written moments with emotional impact and outstanding twists sure to leave you with your jaw on the floor to scenes with clumsy dialogue and ideas that just didn't work out as well as I would have liked, though exactly how much of this inconsistency can be put down to translation issues is hard to judge. (wolfsgamingblog.com)