That wasn't a break up. A break up would have actually been better for Yutaka. And Yutaka already had good memories. A break up starts ugly but it allows for both parties to start to realise that it ended. Yutaka wasn't given such opportunities
I don't know if someone cheated on you or ghosted you, but the psychological aftermath of that is hell, both for the present you as well as for future relationships. Specially when you have the handicap of growing up and living in a society like Japanese society.
As a bi person, I have always thought that the uncertainty that some gay people quote as the reason for not dating bipeople is underhanded. Do you think there's no uncertainty in a bi person's life? A relationship needs work on both parts and blaming the bi person "bi-ness" for the state of the relationship is really bad for both parties involved.

I kind of understand why Maki chose to break up with Yutaka that way. Because in that situation, if Maki leaves behind even one endearing memory, it would be harder for Yutaka to move on. BUT HE WAS STILL AN A-HOLE for blind siding Yutaka. I feel people who do this are cowards and has their names on Satan's list of souls to burn, or should be hit by a bus.
It's a conflicting feeling. As a gay person, you tell yourself to not for for straights, or bis.. because every minute will be filled with uncertainties of the future.. but that's not how it works. The heart wants what the heart wants. In truth, I prefer this kind of break up. Be it the other person cheated or you just drifted apart.. I don't want to hear the words "I'm sorry" or whatever bittersweet words you would throw in just to smooth over the conversation or make yourself less guilty.
But it's still sad.