I really like fanfiction. Reading and writing it. Nobody in my life knows and I plan on keeping it that way.
Here’s another way to look at it, then. By popular definition, an agnostic person believes that there is no ontological proof for the existence or non-existence of God, or the divine. The agnostic person is thereby operating within the conceptual framework of religion. (A lot of agnostics in the Western world are agnostic specifically about the existence of the particular God of Abrahamic religions.)
On the other hand, atheists are simply not concerned with or do not recognize divinity, as a concept. In a way, it’s like how nobody holds an affirmative belief that Spiderman does not exist as a real human, because superheroes are categorically fictional, and it’s not even ontologically possible.