Responses
I think you got this manga all wrong. Eto and his wife are nothing but friends and business partners, who used their marriage as a lure/cover to boost their business. They act the part in public, but I'm positive they never slept together. I think dorishpp's comment says it all.
Exactly right
it was OK. All the characters are acting like marriage is not that big of a deal, kinda annoying. But at least they stop cheating and break off for good.