That literally only just happened this chapter and it honestly feels out of character for Nadeshiko because she's been so open-minded in every other chapter. Before now it's been perfectly reasonable to imagine our three main characters uniting in a polycule and fighting Nadeshiko's weird Dr. Wily mom lol
How so? Nadeshiko has almost from the very start felt bad about this, even as she's tried to be more open-minded as her function as a sex robot dictated. She did indeed offer sharing Akane when she first met Jun, but then immediately realized she could not do it.