Love is blind, love is madness, there are no limits for it, be it in good or bad way, because of those stupid feelings that the humanity experienced hardships, mischiefs, dramas and more shits but at the same time we continued to exist much longer and more advanced than any other species because of those feelings, those good side and the lessons of bitterness from the bad side of those feelings.
The thing is, when two ppl are in a mutual relationship, it is their job to protect their love. There are those who are bathed in arrogance, self-centered, having high self-esteem ego, one-sidedly blame all the faults on the other person, those people never take responsibility for themself while thinking they are the right ones, etc... when a problem in the relationship occurred, it is both sides' mission to try to understand the causes and find solution for it, and most importantly, to understand each other more. But for Kaoru and her husband's case, we can clearly see that they are unwilling to open up their hearts, they hold distance from themself, they keep things as secrets with the excuse like 'i might hurt the other person if i speak it out' but in fact they just severe their relationship by doing that. Then cracks appear in their relationship, soon it will break apart if this goes on. If Kaoru ends up divorce, it's her fault not being able to fully understand Reiichi and the same fault goes for Reiichi's side. If Kaoru ends up in love with Uta, it's Reiichi's fault for not being good enough to gain Kaoru's love and again, the same goes for Reiichi if he ends up with Risako, it is Kaoru's fault for not being good enough to gain Reiichi's love. Kaoru and Risako are acting as a trial here, if Kaoru and Reiichi's relationship are solid enough, nothing will happen, as people called 'devoted love', i know it is wrong to have feelings for someone who has married but hell no, controlling your feeling of love is no joke matter, you can see just how it tormented Uta(poor Uta...). No matter how you look at it, they are both right and wrong, this conflict is what that makes the manga's plot good or even bad for some people, but judging on the serialization and the readers' reactions, majority of readers can enjoy it.
To sum it up, blame your self if your relationship goes wrong, don't put it on others! *insert a lot of angry noises*