Kayo is a horrible person. But that does not mean Kayo did not actually have real feelings towards MC.
I don't think Kayo ever saw MC as a backup when they first started dating when they first started high school.
I don't disagree with this, she accepted dating the MC after all. Yes, she loved him at the start, we both agree on that. The problem is, you assume that feelings don't change over time, no matter what she does, and say she still hold the same feelings at the start. But I don't think it is the same when Iketani entered her life once more.
That was my point from the start: She already lost interest in MC. Her longing for him now is only a result of the pregnancy which she didn't want to have.
I don't think Kayo ever saw MC as a backup when they first started dating when they first started high school.
You missed my words. It was MC who felt that way, not Kayo. Kayo stopped paying attention to him when she accepted Iketani. She was too focused on Iketani to have such thoughts while MC was just "there".
I think it just ended up that way when Kayo started having sex with Iketani again.
Correct me if I'm wrong but I interpret that statement as "Kayo's feelings for MC changed WHILE she was already having an affair with Iketani". As if to say, it didn't change yet when she just cheated for the first time or when she just decided to do but not have done it yet. As if to say, she didn't have strong feelings towards Iketani to decide to accept him but still decided to have sex regardless.
It is precisely that she didn't hold those same feelings for MC that easily accepted Iketani. As Napolitan explains, MC is like a property and "air" to Kayo. Kayo needs MC to breathe. Whatever Kayo does, MC accepts, MC forgives. Kayo does not need to reciprocate. We need air to breathe but that doesn't necessarily make us "love" it the same way we love our favorite things.
You say that actions speak louder than words, but Kayo originally refused Iketani when she was dating MC. It was only later that Kayo finally gave in and started cheating.
So the initial refusal at the time makes her "actions speak louder than words" despite her eventually giving in? If her actions really spoke louder than her words, she would avoid seeing him altogether and consulted with the MC, her boyfriend, about her troubled past. But why didn't she do that? If she could refuse at one time, why did she instead choose to cave in to her desires?
If MC is "the only one she needed", why didn't she call onto him for help especially during the time when their relationship was at stake? Now you see why those words lack sincerity when she conveniently used them only to overturn her situation.
Manga made it clear: Kayo broke up with Iketani in middle school. MC asks out and starts dating Kayo at the beginning of high school. Iketani pursues Kayo to restart their relationship. Kayo initially refuses and stays loyal to MC. Eventually, Kayo gives in after some time and starts cheating with Iketani.
You are right on this. My initial assumption was that Iketani approached him at start of high school but got ignored because she started dating the MC then it was only after some the time when she started admiring Iketani again that Iketani continued wooing her again.
It wasn't that Kayo wasn't interested in MC. It was that Kayo and MC were on two completely different levels. Kayo was always going to feel disappointed with MC.
So what was that "interest"? When did it show? If she was so disappointed with the MC, why did she not break up and instead choose to cheat? To me, it just sounds like she wasn't even interested enough to care about breaking up if we go by this statement.
Kayo's relationship with MC was doomed from the start. They were childhood friends that were basically like siblings, suddenly having to relearn to be lovers.
Yet Kayo failed to understand MC's feelings? Sounds like she needs to relearn being a childhood friend/sibling as well. Sure, siblings/friends don't necessarily understand each other well. So if being lovers failed and so did being friends, where is the "love"?
Kayo was already very experienced in dating and sleeping with someone that was also very experienced. It would be like competing as a professional, then suddenly pretending to be a complete amateur.
Yet Kayo cheated and failed to break up with MC? And you say she's very experienced? More like experienced at sex.