It looks like the phrase could refer to a few different things. To help you best, I've outlined the most likely interpretations:
This might be a tagline for a dating or social app focused on "mature" connections and romantic narratives. us sex matures
You might be looking for a review of a specific novel, game, or series that uses this exact phrasing in its title or description (possibly an indie game or a niche romance novel). It looks like the phrase could refer to
Could you please clarify if you are looking for a review of a , or if you are interested in a general analysis of how mature romance is handled in US media? Could you please clarify if you are looking
You could be looking for a review or commentary on how "mature relationships" are portrayed within American (US) media and romantic storytelling generally.