Iam confused. Uke said that he transmigrate into the novel but why this like a reality

Its the same in every transmigration plot, before it was fiction but now that MC is inside the world it becomes real, like when characters that didn't originally appear come out and things like that, they might not be "real" in the frictional world of a novel, but they're "real" in the world of the novel that they live in

It means that the novel/game setting he's in now is his new REALity so yeah, anything can happen there now just like how life is truly unpredictable