Yes, the novel is completed. You can see groups translating here https://www.novelupdates.com/series/diamond-dust/
or a new link here https://sites.google.com/view/honeebuni/dd-all-chapters
Spoilers!
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They do indeed break up, but for good reason, ML fucks up, big time. But I love that there is a lot of accountability, it is not rushed, when they do get back together it is after a lot of growth on both sides! But it has a very happy ending!
Ah I haven't read the novel completely, still halfway but if they do break up that would be better. Distance can make them realize their feelings more deeply. And oh my ghad you should try reading the novel, it's a much different sensation than the manwha. Manwha is hot but novel is scorching. Plus their feelings and thoughts are more raw and conveyed in the novel. I'm addicted. I love a good story with a good plot and a more better main characters. I love them so muchhhhh
https://sites.google.com/view/dd-dark-mode/dd-all-chapters?authuser=0
Here if ever you want to read it. I just got it as well from the previous comments. The translation is really great unlike the first translation I've read.

Kinda regretted I read the novel first because of my impatience, just a little bit. I should've enjoyed their first timeeeeeeee like visually without me imagining it first HUHUHU I'm a pervert, yup.