I don’t think it’s about his infidelity but more about how they are a team and and need each other. They don’t love one another but have to stick together. But because of that they decided to sacrifice a love life. Maybe they should have an open relationship, I don’t know
But that doesn't change that infidelity is also a part of this story.
Also I'm glad they are together, living their miserable life with one another because I really don't main characters
Also this was so realistic, if we see what happens in Japanese society, it's similar most of the time.
Honestly, I don't really know if the story corresponds to a manga. Let me explain: it’s terribly realistic, cold reality. It's a story about a couple who spent their honeymoon where one of them made a mistake and the other must forgive them. This is not a funny story. It’s a frustrated story of a perfectly imperfect human.