Kai, who is studying oceanography at university, is a perfect person with excellent grades, a fine pair of eyebrows and a promising future. However, he is fed up with the noise of his all-male family of six and longs for the tranquillity of the deep sea. One day, during a family dinner, the suspicion of Umi's virginity is raised. When he gets the wrong idea, he decides to make a girlfriend who will let him have sex with her as a temporary measure... Is the love that Umi encounters a chance encounter? Or is it fate? A slightly naughty and cute love comedy!