There is a YA novel called “Tash Hearts Tolstoy” with a heroine described as “a romantic asexual.” Many of the asexual characters I’ve found on lists are in YA novels; m/m romance; or fantasy and SF. For example, lists have suggested some of the following in SF and fantasy: the MC of Ann Leckie’s Imperial Radch; Every Heart A Doorway by Seanan McGuire; Banner of the Damned by Sherwood Smith; and probably Paksenarrion in Elizabeth Moon’s “The Sheepfarmer’s Daughter.”
In recent SF reads, I have read almost all of the Murderbot stories by Martha Wells. The narrator is Murderbot, a security unit (SecUnit) designed without gender. Murderbot hacked into its governor module and gained control over itself. But instead of killing humans, it continues to do its job and save them from themselves. :) When it has a choice, it would rather just watch its favorite soap operas (particularly “The Rise and Fall of Sanctuary Moon”), fast-forwarding through any sex scenes. I think Murderbot might count as asexual, although you could argue that it did not have a choice in that.
There is also a Jughead graphic novel that acknowledges his asexuality. Many fans were upset that Riverdale changed that aspect of the character.