So the prompt here is that during some sexy time, the male nation decides to do some breast worship and titty play stuff, and he ends up breast feeding or getting the fem!nation to lactate or something along those lines and discovers that wow, this stuff is actually pretty good. Of course it makes the fem!nation feel good too, so when this becomes a regular thing they don't get super weirded out.
However, nations have magic breast milk, and it's basically drugged the male!nation into being very submissive and super loyal to fem!nation, but they're also addicted to it.
Anon would really like to see a couple from Tomato Gang or the BTT. The fem nation can be one of the originals or from nyotalia, it doesn't matter.

Bonus- magic boob milk also has weird side effects (up to author anon)
Bonus- one of those side effects is weight gain (I mean the stuff is meant for babies to put on weight sooo that's not a huge stretch)
Bonus- lots of breast and body worship if smut scenes