That's fucking cheap author. Demonizing her childhood friend so we will feel sorry for Nanase for having that kind of friend and prefer seeing her with a cheater. That's cheap.
At the second Yuni had some feeling for Fuuko, her romantic relationship with Nanase was dead. The only who still believe in that relationship is Nanase. Their couple is just a masquerade.
I'm still rooting for her childhood friend even though there isn't a lot of chance they will end together.
Nah, this wasn't a cheap shot - Yuni's still a cheater who didn't like that Nanase never paid attention to her; she and Nanase shouldn't be together just because Yuki's a historically manipulative jealous & possessive bitch.
This just shows that Yuki's not "merely a concerned friend" in all of this and actually has selfishly hostile intent toward the couple.
And I guess it provides a bit of additional context as to why Nanase seemed to hide the fact she and Yuni were together from the entire world at large -
And it was entirely due to the rumor mill started by her "childhood best friend".
Though, that still doesn't absolve her of being almost laughably ignorant of Yuni's feelings during their relationship, to the point of continuously sidelining her in favor of Volleyball and/or Yuki. Yuni fucked up by cheating and is shitty for that, but it's all contextually related, in the end.
Truly there are no morally upright characters in this series.
That said, Nanase and Yuki deserve one another. Though Yuki seems possessive to the point that she'd freak out if Nanase went off with any other girl friend/teammate on some function, and I have to imagine she'd go so far as to start isolating Nanase and driving her toward eventual misery, given her thought process and actions shown in this chapter.
