We're a married couple entering our tenth year... It turns out my wife's actually having a secret "second partner" relationship with Aoi, the neighborhood association officer. You know, a "second partner" - a term for an extramarital affair. Despite both of us already having partners, we've been continuing this neighborhood affair to satisfy our sexual desires as "second partners." There's no way we can stop, because we're completely addicted to her incredibly erotic sex.
