Fuyuki didn't believe the lies. She had full faith that while Eri can be a little insensitive, she's not one to talk to someone like that. Also, the bigger point, Fuyuki had no problem telling Eri that she was dating a girl and Eri accepted it just fine after the initial shock that Fuyuki was even dating. So the only issue that Eri has had with girls dating was her bad experience with being persona non grata for something she didn't even do.
I'm planning on going back and re-reading the entire series again once it completes; I first found it with the posting of the previous chapter, and read the whole thing over the course of one night which has very much probably left me with not the clearest picture of all the events and thus requires a repeat read-through to fully digest everything.
That coupled with my seeing parts of myself in Fuyuki meant that I wanted to take her side in things, which very much gave me a biased view of the other characters in the story. And none of them are bad, or villains, or antagonists - not even the classmate with whom Kyou cheated on Eri with, at least in a certain sense.
Which, makes this a great story I think - each character is sympathetic and complex and there's fault in all of them, but reasons to root for their eventual happiness as well. And I'm grateful for this specific series of discussions because it's reminded me to step back more often and consider things outside of the narrow focus I sometimes adopt with manga, because of the titles I'm often reading that have a more black & white, clear-cut view of who's who in the narrative that this specific title effectively transcends.
And it's why I actually quite like this chapter, because even as Kyou did some very hurtful things to Eri and to Fuyuki at various points, it's clear that it wasn't some sadistic, malicious intent on his part wherein he was seeking to destroy their happiness. He was simply acting like a human being, in all the selfish, self-focused ways that entails, and he also stepped up and is trying to own up to the mistakes he made, while even understanding that "forgiveness" isn't something he's owed for doing so. The shared confessing to both of their faults in this chapter is refreshing to see, just from a growth standpoint that makes me want to seek out more manga like this title simply for the refreshing take on the complexity of relationships between characters that is portrayed here.
And I very much look forward to Eri and Fuyuki finally having The Talk in the coming chapter(s), because I very much want to see if they can find a path forward that sees them not have to give up the most important person in their life, if not potentially forge a deeper connection.