This show could have been more interesting. The best part was the cinematography. While not anything spectacular, it felt calm and cool, like a nice movie. Someone said so in the comments, but this would have better served as a movie than a show. It didn't need 10 episodes, however short they might be.
Story spoilers ahead, read on at your own risk...
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So the major plot point is that the two of them can't do something which is a major part of most married couples lives: have sex. And with that, have children.
This is a real issue that affects many men and women, and in this case, it appears that Kumiko has vaginism. However, this was never stated outright within the drama. In fact, she and he never went to the doctor to do the obvious: find out what the issue was and see how they could overcome it.

Instead, we're given a very strange story arc that involves their continuous cheating on each other. First, Kenichi with a number of prostitutes every Saturday for years on end. Second, Kumiko with an online site that is a hookup spot. Kenichi is constantly asserting that sex is not love and that he doesn't need sex, yet it's never clearly spoken about that he constantly goes to a brothel. Kumiko mentions it briefly once, though she takes most of the blame for never revealing the fact that she was not in fact a virgin.

The show ends in a very lackluster note. Nothing is solved. The entire plot seems to be saying, "it's okay the way we are", but then why make this show? Why show this particular couple? What is the point? I love an open ended plot, but this show just seemed to be meandering this way and that, with no particular direction. It was stretched out to 10 episodes to say, "it's okay to be the way you are and love each other this way," but we don't need 5 hours of screen time to do that. Even if this was a movie, the current plot is too lackluster to remember. Very forgettable and no lasting impact.

This show wants to convince the viewer that Kenichi and Kumiko have overcome a problem together, but all I see is two people fumbling without properly addressing a problem or trying to solve it, then saying "let's move on." The resolution is not convincing.

This show could have been much more, but too much time was wasted on repeating the same actions, intermingled with Kumiko's obtuse thinking and communication issues, and Kenichi's lack of commitment to the issue. I'm not even sure who Kenichi is, by episode 10, as he was fairly flat the entire time. He was enigmatic from the beginning, and I wasn't convinced Kumiko actually liked him when they began their relationship. In fact, he was quite weird, just sort of embedding himself into her life without much explanation. And she just sort of quietly accepts it all without any questioning. She seemed like she was just going along with the flow as things happened to her. She wasn't really a part of anything, she just let things happen. Kenichi only did actions, and Kumiko only received them. That was their relationship for 10 episodes.

Even Kumiko's interactions with her students, particularly Miyuki, seemed to have been out of place. She quits suddenly, and that portion of the plot is simply wiped clean off the board. Then, oddly, she visits the home of her former student, but I'm not convinced she even knows why, or even the writer. Nothing was completed or fulfilled by her visit. Simply the satisfaction of entering the house and learning a little more about her. I feel this was underdeveloped and rendered useless..

Wouldn't rewatch. Can't really recommend. This was just a lackluster show. The filming was pretty, though. The acting, was somewhat mediocre. Maybe slightly above for Kumiko's part.