This will they/won't they is really tense, enjoying it so far. I'm hoping the author still pulls a vanilla ending out in the end and all of this is just (admittedly compelling) teasing, considering his previous work. Maybe they get some unresolved issues aired out and their relationship is stronger for it, at least no sorrowful break ups. (Maybe they just come out of this swingers and get married or some shit).
@TheLastTLK
This page ---> https://mangadex.org/chapter/789349/19 implies that she (Amane) came over at the same time as Miko, as of now I would think that rules out anyone cheating yet. Though we'll probably see in the next chapter or so Miko trying to put the idea of swinging in Amane's head, since the other implication is that they were together at some point before everyone ended up in the apartment. May explain the ignored txts as well.