Hello! A person who is sex-neutral is someone who has no strong feelings about sex. They don't see it in a negative nor positive way, they're just neutral about it.
Wren, Galvin and Lonan are all on the asexual spectrum (Wren is demisexual, Galvin is graysexual and Lonan is asexual) and all 3 of them happen to be sex-indifferent.
However, not all asexuals are like that. Some asexuals are sex favorable while other asexuals are sex repulsed. Aces have different experiences, it depends on the person.