I believe the structure of this story is for Dongtae x Eunju. If it changes to Dongtae x Mio, I'll be very surprised. My reasoning is that regardless of the similarities between the two, this story has a moral gravitation centre around a person who was rescued by Dice (Dongtae), and a person who recognises Dice for what they are (Eunju). In summary, I think Eunju's existence is a plot device for Dongtae: she is supposed to be a symbol for him of what it means to be good. Right now, she is his only reason to fight.
While I have warmed up to Mio, Dongtae's feeling for Eunju are genuine: he loves her, has always loved. It may fit it beautifully in our minds that people with similar backgrounds end up together, but who is to say that, below the surface, Eunju isn't similar to Dongtae? Morally, they seem to be on the same page. I'd find it awkward if in the end he is not rewarded for his efforts by earning her love. In a sense, it would make the story neater. If he doesn't, what was the purpose of Eunju in the story?
I believe Mio will end up learning something about herself. Her personal journey is different from Dongtae's. And who is to say that the two would have fallen in love with each other if they had known each other before? Actually, it happens just as often that in situations like that, the partners try to use each other as an emotional crutch. Dongtae fell for Eunju because she treated him with humanity, and now he has the opportunity to do it to her in return.
I am not fond of "back to square one" endings. I think they defeat the purpose of the characters' struggle. I know there is no poetic justice in real life, but this is fiction, and everything in this story points to poetic justice in the ending, so I'd prefer if it remained consistent. I would be left with a taste of "so the ugly kid cannot win the beauty after all" if everything ended as it began. I'd prefer this to transcend beauty, and Dongtae to achieve what he wants - Eunju - by doing what she herself says is her goal in life: working hard with what she has been given. Dongtae has been given a heart worthy of hers, and he is struggling towards that end, I wouldn't like it to be thwarted.
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In an unrelated matter, have you noticed that the mysterious Die seems to have changed since its first appearance back in chapter 48 or so? I was reading recent chapters again and noticed that when Gilma showed it to Daewoong the number in the visible face was 1. In more recent chapters, it is 2?
Either this has no meaning, all faces are numbered 1 to 6 and it is just a coincidence drawing by the author, or it has meaning.
If it does, it probably has to do with Gilma's saying that the Die will change every time a new A Ranker is created until there are "enough". I don't know how much is enough, but between chapter 48 and now, one A Ranker has indeed been created: Sungchul. Did the number change in response to his entry in the A Ranker tier?
If that's the case, I'd say the meaning of this has to do with Mooyoung's goal. Maybe his goal is to kill a representative of each A Rank skill? We know he killed three people when Taebin escaped: a Flyer, a Psychokinetic and another one whose skill we don't know. Taebin has Teleportation, and Daewoong has Cloaking, to Mooyoung's own Time Pause. So Mooyoung just needs to kill two more to achieve his goal, if that logic is correct.
And maybe the Die will indicate a 6 when there is one representative of each skill alive at the same time? And maybe that is what Mooyoung is trying to prevent? If that is the case, Dongtae is not a target (his skill being the same as Mooyoung's, his death wouldn't change the situation), but Taebin, Gilma and Daewoong are. Right now, only a See-through Vision user is missing (Mio?). But that wouldn't explain why the number is still 2: maybe it has something to do with being "Chosen", as Gilma alluded to in chapter 54 and when he said Dongtae was a special target for the Hunt?
Just random ideas, couldn't resist.