Mitsuki or Haruka?

Mitsuki all the way. I think this anime was meant to be a more adult and realistic story than most. And I personally don't think any of the characters are acting beyond the pale.

In my opinion, Mitsuki's actions make perfect sense. She and Takayuki both liked each other originally. The whole reason Takayuki is apprehensive about being with Haruka in the first place is because of Mitsuki. Couples form and bond over shared tragedies all the time. It's completely natural for a person to get insecure over what is essentially an emotional affair, and later becomes a romantic affair when Haruka and Takayuki start making out again.

Mitsuki says she doesn't want to be Haruka's friend anymore because she's an active threat to their relationship, and she wants to create distance between the three of them. When that boundary is threatened, she tries to forbid him from seeing her. Immature actions sure, but completely believable given the situation. And honestly it's up for debate whether detached sex is worse than emotionally bonding with your former lover.

The worst thing that Mitsuki did was try to pressure Takayuki into telling Haruka about their relationship. It's a reasonable demand normally, but given the situation that would have only ended horribly. The medical staff and Haruka's parents were the worst people, for essentially forcing Takayuki into an emotional affair, something that is clearly insane to ask of an active couple. At the end of the day though, Takayuki failed to uphold proper boundaries in that context.

Everyone needs a girl like Mitsuki to pick them up when the chips are down. While I liked all the girls, I definitely appreciate this being the canon pairing in the anime. It would have been nice for the group to remain friends at the end, but that would be unrealistic and very difficult to manage. Ex-lovers rarely work out as friends, especially right after a breakup. It makes complete sense why they moved away. I just wish they commented more on Takayumi's original feelings for Mitsuki because those were essentially forgotten about in the series.

As for the other girls: Akane comes next, as a mixture between the two. I was surprised this was never touched on. Then Daiguuji. We don't really get any time with the rest of the supporting cast that interact with him, so Haruka comes in at 4th. They didn't have much in common or a whole lot of chemistry to begin with, and even the original relationship felt like it existed more because it was easy than anything else. Normally I would choose Haruka's role in similar anime, but I think she was incredibly weak here (no pun intended). I'm definitely biased though because Mitsuki is 100% my type, and it's a shame she cut her hair. Don't get me wrong, the short hair still looks great, but I liked the long hair more.

P.S. I realized I never mentioned the friend's love angle. Yes, it is a bitch move to go after someone a friend is interested in or was in a relationship with. But I honestly don't care all that much. At the end of the day, if you really care about someone, you want them to be happy, even if it's not with you. And if you feel really strongly for someone, I don't think it should be a crime to confess to them or go out if your intentions are pure. It would be a different story if Mitsuki didn't care for Takayuki. Without Mitsuki's help, Haruka would have never even asked him out. So in a timeline where Mitsuki doesn't help her, she'd still be betraying Haruka's feelings if she acted instead. And Haruka also suspected that Takayuki and Mitsuki liked each other from the beginning, yet no one levels the same criticism at her. That point is a wash in my opinion. It focuses more on the jealous idea of, "if I can't have them no one will," then what's actually best for everyone involved.

Also, even putting the sex aside. I think we can all agree that Shinji is a trash friend. Yes, people can start moving faster out of sheer survival if left alone during a crisis; but it's always best to share the burden (responsibly) and and move forward together even if it takes more time. If you've had to go through your lowest points alone, you already understand this intimately.