I like that after some time, it came to the point that everyone is kinda fucked up, and people have to weigh in their own hearts everyone's faults to decide who to root for.
Yuni is a cheater, but she was also seemingly completely neglected by her so-called girlfriend. That neglect, on top of the fact that she has a tough home situation, where she has to do all the chores, and stay late even to see her own mother, her only companion, a sickly stray kitty, passing and traumatizing her even more, makes her behavior, especially craving attention and affection, more understandable. Redeemable? That's what we all need to decide on our own.
Nanase is an awful partner. I don't think she ever went out of her way to do something for Yuni. She ignores her at school, leaves her hanging for club activities, to the point of even forgetting their anniversary. Shows up with Yuki to the university tour, and proceeds to mostly ignore Yuni and spend time with her friend instead. And that's how she behaves right after being confronted with her partner cheating and still deciding to do better and win her back. She doesn't, seemingly even refuses to, understand Yuni's needs, partially because she had a virtually perfect home life, with both parents, siblings, and doggies to keep her constant company. And she, in multiple situations, allows a friend whom she knows her partner is jealous of, get too close to her. Is she a bad person? I don't think so - she seems mostly naive and ditzy, like her mother said. Despite her competent, princely demeanor. But she is definitely an awful partner.
I can't be bothered to write a paragraph about Fuuko and Yuki - Yuki is a bitch, self-righteous hero-complex home wrecker. Fuuko is, well, a mostly self-aware, playful, kinda evil, but in a very alluring way, home wrecker.
So everyone is awful in a different way. Great fun.
I'm not sure if I'm leaning more towards rooting for Yuni getting with Fuuko, or Yuni and Nanase finally understanding each other better and mending their relationship. Realistically, I don't think Nanase's character would allow that to happen, but it's a work of fiction after all
