I don’t really understand the point of the ending. If they had gone their separate ways, it would have made sense. But instead, Ruki just accepts being cheated on, mistreated, and talked down to. Especially later, when Sacchi mocks her with the same girl she cheated with. Not gonna lie, the ending felt pointless, like the author just wanted a bad ending for the sake of it. And everything suggests Sacchi will keep cheating.