For starters, the protagonist lives as a male for the first 20 years of their life, and in the course of the novel they have a long-term relationship with a cis lesbian, as a woman, that includes discussions of whether they truly are a woman or if they were just tricking her. At other times, they have casual sex as a man with other men, but never anything deeper. Also, throughout, the narration only ever calls the main character "Paul" and "he", so their female identities always seem more precarious than their male ones, even though they seem genuinely happy and more fulfilled in them, which is very transfem in my view.