Not only it is bad, it doesn't answer anything. He broke up with her. Good. But what has changed during that 5 years to warrant the "i would do things differently?". Is he willing to let her fuck others now? Did she manage to fix what was wrong with her which ultimately doomed their relationship? Lets be honest. Miko's condition is the sole reason of their break up. But we still see the ending through his perspective when EVERYTHING related to any possible "good ending" starts and ends with Miko. Unless, as i said, he suddenly decided to be fine with her getting railed by other man like how he was coerced into in the beginning by the very same Miko.
It was a not an open ending. It was a no ending.
I'm going to start by saying that we agree.
An open ending has to give you enough elements, as a reader, to interpret what happened in different ways or imagine different plausible consequences. It's not simply about leaving a story unresolved. Let's think about some famous open endings:
Blade Runner gives you something to think about regarding identity and what makes you human, through the question of whether Deckard was a replicant or not.
Inception, when the spinning top starts spinning and makes us wonder whether he is still in a dream or is actually in reality.
The Thing: two people are left at the end. Either they freeze to death, or one of them is the Thing and will eventually kill the other. The movie doesn't need to resolve it, because in horror, mystery, or suspense, leaving something completely unresolved can be much more disturbing than explaining it. The unknown can be more powerful than a concrete answer.
The problem with
Soredemo is that its premise would be: "Can a modern relationship survive without sex between these two people?" But for an open ending to work, you first have to properly build that relationship and that conflict. And for me, this is where the first problem appears: the relationship between the two protagonists is almost nonexistent for a large part of the manga. As readers, we don't have a sufficiently clear understanding of their motivations, what they actually feel for each other, or why they want to maintain the relationship. If the only answer is "because they are in love," then the conflict loses much of its strength.
In the end, they break up, five years pass, and they meet again. But their fundamental problems are never resolved. There is no new information that allows us to reinterpret their relationship, nor are there different possibilities that we can consider as readers. The relationship simply ended, and the manga ends without resolving the conflict it established. To me, that's not the same thing as an open ending: it's leaving the conflict unresolved.
The fact that the author doesn't tell us what happens next doesn't automatically make it an open ending, if there is nothing to interpret, then it's simply something that Miike Kei has decided not to tell us.
An open ending is a tool that allows the writer to play with the reader, giving them enough elements to interpret or complete the story for themselves.
