I wish the "he cheated!!!!!" crowd gave it a rest. If you look honestly at their situation they were essentially strangers, a company robot and her live-in housekeeper with their "marriage" being nothing but a pair of matching rings. Those last two chapters were a beautifully written heart-to-heart, let's not spoil them.
No, I understand. In a society where divorce is an option for both people, if you're unhappy, just leave. You guys are strangers? Be strangers with different last names. I know I said I wasn't gonna harp on it, but I don't want to downplay what he did by acting like it's reasonable, either. Ultimately, he was only willing to leave when he thought he might have something better lined up. It was a selfish act that we shouldn't try to justify just because we don't like the person it happened to. If anything, I feel like people are too quick to condemn Kaede for being exactly who she decided to be in the beginning of the relationship, openly. She's guilty of being emotionally negligent and unempathetic to her life partner, and not breaking it off once she realized she wasn't being an equitable partner to him. He's guilty of being undiscerning of his own needs and for holding these unspoken expectations of reward and letting them fester into resentment. I think lots of people can empathize with these states of mind and the mental toll they take. But it's for that exact same reason that so many can openly condemn cheating: because the rest of us didn't cheat. Like you said, though: this story handles it beautifully, without condemning nor justifying, just contextualizing, but that doesn't mean others won't come away with their own analysis especially when just speaking to the general circumstances.