*****SPOILER AHEAD**********
So technically, the novel isn't listed as yaoi. But there isn't really a whole lot of other romance going on in it either. It's mostly family love. Now, having said that, there are a LOT of hints of a possible gay romance happening in it. Throughout the entirety of the series, there are words like '**name withheld** will die at the hands of the person he loves the most.' and more, though it's less words and more actions, like a certain someone decides to travel throughout all of space for years just to save another certain person, both of whom are men.
Now, the novel is written in a very specific person's perspective, which means not all the details that are there can be listed as 'true', and there will be instances in which the story's perspective can't actually show all the relationships between the characters. Therefore, there are a lot of people who believe that it can be read in such a manner as yaoi. You can also read it as a family love, or whatever you so choose. That's the true beauty of this story. The authors(there are two for the novel) stated that the story was designed to be read and interpreted as the reader wished, since this entire story is all about the 'reader'.
Personally, I interpreted the relationship between Dokja and Joonghyuk as romantic love, albeit slow paced in some instances. It's hard to even really call it romantic in my eyes since it feels more like a soulmate type of connection; basically, to me, there is something that runs much deeper than just simple romantic love in their relationship. You'll see what I mean the more this story progresses. To call it yaoi...would be disrespectful, as I feel most yaoi include sex at some point, or make the sexual relations (I am including kissing in this) a key part of the story. The relationship between Dokja and Joonghyuk is the kind of love that you rarely get to see, regardless of the genders in the relationship. Their relationship, and this whole story, is not something so cut and dry as to be able to label it under a category.
I would personally suggest you read the novel, as you will NOT be disappointed. Even with the awkward translations to English, the story stills comes across to inspire many readers and touch our hearts. It is truly a masterpiece of a story, at least in my opinion. I've read a lot of books, of all different genres, and yet for some reason, it was this novel that had me continuing to think deeply about it long after I had finished it, and it was this novel that I keep in the back of my mind, wherever it is I go.
ITS A HAPPY ENDING. Or an eventual happy ending for those who want a more detailed or an "aftermath" ending. An vague explanation (Srry if its bad): if u read the last chapter, the hints are pretty obvious that Dokja is alive again. One of the hints is when the "king of the kingless world begins it's storytelling" (only Dokja has that fable in the 1864th worldline) and the star stream functions are working again. Before, the star streams system functions were gradually fading, at the time same time Dokja was alive nor dead and the only thing that hsy's fable that she got from Bihyung (?). Dokja is also the oldest dream who keep things going, and that would also include the star stream (I think, plz I don't have enough IQ to understand everything TOT). So the groups fables and other stuff working again out of nowhere would mean that smths changed. It's Dokja. He was OD so he has some significant influence over star stream. The system instantly working again would mean that all of Dokja is now in this worldline and ofc awake. If anyone thinks this explaination is wrong or wanna add on, write it in the the replies. Anyway someone plz pay for my therapy it feels like I went through world war 3