Marin Hashimoto, known as Marine in the English localization of the anime, is a minor supporting character in More Than a Married Couple, But Not Lovers. She is a fictional character from a social game within the story, and she is referred to by Sadaharu Kamo as his two-dimensional wife. Her background is tied exclusively to that in-universe game; she does not exist as a real person in the world of the series. Her personality is not developed in any depth, as she appears only as an object of Sadaharu's affection and a representation of his deep immersion in otaku culture. She has no personal motivations, goals, or agency within the narrative. Her role in the story is limited to reinforcing Sadaharu's character as a passionate gamer and fan of virtual characters, often in contrast to the real-world romantic relationships explored by the main cast. She has no key relationships with the main characters beyond Sadaharu's one-sided devotion, and she never interacts with any real character in a meaningful way. There is no character development for Marin across the series, nor does she possess any notable abilities. She remains a static figure within Sadaharu's hobby and one of the minor background elements that highlight the different perspectives on romance and attachment among the student body.