哲郎(三浦友和 饰)和亚纪(渡边真起子 饰)虽然过着同居的生活,但他们和普通的情侣不同,实行的是开放关系,彼此之间并不过问干涉对方的私生活。哲郎有过一段失败的婚姻,和一个现年8岁的儿子俊介(伏屋博雄 饰)。前妻不幸遭遇了车祸无法照顾孩子,于是俊介便来到了哲郎和亚纪家中暂时生活一段时间。 虽然对于俊介的到来亚纪并没有发表太多的意见,但心里却十分的不开心。不仅如此,叛逆的俊介和亚纪之间的关系非常的紧张,他一直觉得是亚纪从母亲身边偷走了父亲,令自己得不到父爱。在一连串的意外和波折之后,俊介回到了母亲的身边,但哲郎和亚纪还能够重新开始曾经的生活吗?Tetsuro is living with his young girlfriend Aki in a pleasant house in Tokyo. They both spend a lot of time at their jobs. However their routine is upset when Tetsuro brings his 8 year old son Shun to live with them, while his ex-wife recovers from a car accident. Aki is annoyed because she was not asked, and she knows that she will have to do the bulk of the work in caring for him. This forces Aki to reevaluate her relationship, and decide whether she is to remain a modern working woman, or become a mother.