chinese translates roughly to:
you are this/the
protagonist of the story

你是 = you are
這个 = the (but 个 is used as a kind of extender/measurer to define a quantity)
故事的主角 = story protagonist/main character

the way i kind of read it was like "you are this: the protagonist of the story" but also i don't know chinese outside of xhs memes so take that with a grain of salt