Kōsuke Mihara is one of the four central characters in the anime Married Couple Swap. He is the husband of Asuka Mihara and a longtime friend of Reiji Suzukawa, having been friends since their student days. The two couples, who have not spent time together since they were unmarried, decide to visit a hot spring inn together. During the trip, Kōsuke initiates and repeatedly pushes for a partner swap, first suggesting the idea and later proposing to extend the arrangement beyond the initial night. His motivations appear rooted in a desire for novelty, curiosity about the boundaries of his marriage, and a calculated interest in testing loyalty. He is portrayed as persuasive and somewhat manipulative, using whispered suggestions to sway Kanade Suzukawa, Reiji’s wife, into agreeing to continue the swap. Kōsuke is also depicted as physically assertive, approaching Kanade in private settings such as the bath and pressing for intimacy despite her initial reluctance. His relationship with his own wife, Asuka, is strained; she is more impulsive and openly attracted to Reiji, which creates tension. Throughout the story, Kōsuke shows little remorse or hesitation, instead driving the narrative forward by escalating the exchange. His key relationships are with Reiji, whose trust he exploits, and Kanade, whom he targets. Over the course of the series, Kōsuke does not undergo significant moral change; he remains the primary instigator of the swap and seems to revel in the control it gives him. His notable traits include his strategic thinking, his ability to read and manipulate others’ emotions, and his willingness to break social and marital norms for his own gratification.