I feel like the only character that i can't possibly understand what their train of thoughts are is risako.. why did she decide to date reiichi if she knew that her best friend that she also has a crush on loves him and that she wouldn't be able to ended up in a marriage with reiichi anyway? Pretty selfish move for me. Now it would be better for kaoru and rei to get a divorce. Seeing kaoru finds her happiness (with uta preferably) would most likely relieve the burdens that rei has on him regarding his sense of obligation towards kaoru. But seeing your ex-wife getting together with your own biological sister is another story that I don't wanna think about for now.