Not sure why Kurumi is getting upset about the fact that Ruriko is questioning her level of commitment. She has treated this relationship as nothing more than a relationship of convenience so far. She comes and goes as she pleases, does whatever she wants, whenever she wants to, and is basically emotionally uninvested.
This whole chapter revolves around Kurumi thinking about buying an expensive appliance pretty much exclusively because it would make Ruriko's life easier. A few chapters ago she dropped everything as soon as she found out that Ruriko was hospitalized, and was clearly distressed because her wife had not seen fit to let her know she was in serious pain and was going to the hospital. Before that, she spent most of a trip to another city thinking about what her bff / wife might find amusing or interesting about the things she was doing and seeing.
She might not be taking the marriage as seriously as she could or should, but she is definitely emotionally invested. In fact, it's often Ruriko who goes out of her way to not get in Kurumi's way. My interpretation of Kurumi's surprise at Ruriko's question is that she has steadily been treating whatever they've got going on as more and more a real, "normal" marriage (why would she care about it ending otherwise? If she was just doing what she wanted, when she wanted, why would she so obviously feel a twinge when the issue of inequitable distribution of household labor was listed as a primary cause of breakups?) and has been losing sight of the fact that it more or less started as a lark (or that that's how Ruriko framed it to her – a thing that could be ended without any hard feelings at any time).
If this story is about anything, it is about Ruriko and Kurumi figuring out together that the fifth rule was a mistake and that their marriage done for lols and subject material for a column is actually real. It seems likely to me that the story will resolve by Kurumi realizing that "somebody else" isn't going to come along because Ruriko is what she needed all along, and Ruriko is going to realize that she needs to come clean about what she's really wanted from Kurumi (real commitment / a real relationship / hot makeouts) this whole time.
I also don't think their relationship is that unhealthy or would have come unstuck in real life. I have seen roommates put each other through some real circumstances, and this is pretty tame, as these things go.
last edited at Nov 8, 2021 4:25AM