Love this chap35! :) Right from the start, I don't like Reiichi for Kaoru. The way he was presented on the early take on was a boring passive narcissist. Nothing seems right in the relationship except that he goes home, eat, sleep and provides financially. For me, he decided to marry Kaoru not because he felt the pity only but there is an angle that Kaoru looks like Risako. The anniversary kissing and hotel suggestion said it when Kaoru dressed up smart just like Risako. Reiichi preference is on sophisticated and smart looking women. That is why there was a chapter, he combed his hair neatly('the trying to impress' look)which for me was to Risako's style and I dont believe on the cheating because Risako was presented to be an intellectual who normally is a strong independent woman. It is so hard to find men who can interest them.
On the other note, I would like to believe that the hand that Kaoru remembered patting her head was Uta's. I think this frame came up from Kaoru's narrative of the past.
Now, it was also presented that Reiichi is also observant. I believed it is possible that he knows that Kaoru is happy with Uta around and vice-versa. Just my take, that is.