By the deliberate actions/inactions of the protagonist's significant other (SO), or by the agreement of the SO with the protagonist, in this VN the protagonist ends up engaging in sexual relations with other people. Only the protagonist (whether they are male or female) has sex with others. Under normal circumstances neither side of the couple has a desire to cheat, but due to the desires of the protagonist's SO, the protagonist will end up having sex with other people. This can be a mutually agreed act with a trustworthy person, which the partner convinces their significant other to have sex with, or a selfish act, with the partner selling or whoring their significant other for personal gain (money, blackmail material on someone, etc.). In every case, the protagonist's SO is (at least initially) fine with the protagonist being sexually involved with other people, and possibly even enjoys it. Don't confuse with Swinging where both romantic partners have sex with others, or Polyamory, which is a long time agreement involving romantic feelings, while Reverse Netorase is a momentary satisfaction of a kink.