There seems to be a few people wondering about the 'relationship' between the two.
Someone put an ask on my tumblr a while back, so I am just copy pasting my answer here:
The whole Nox and Hannes being married is just fan assumption from Ristaccia PV as the scene there kinda indicate the two will ended up together, especially the image of two them standing side by side in their ‘other outfit’ after the scene when both of them hugged and falling into the ‘darkness’. This image has a vibe of King and Queen or Emperor and Empress to it, hence fans speculate that the two will ended up together and ruled together, therefore the whole ‘married’ thing. I don’t know about ‘they might have been married’ part, but more of ‘they could be married in the future’ as Ristaccia PV was said to be the snippet of the story as a whole.
As far as official/confirmed information goes, the only interaction known between Nox and Hannes so far is their brief meeting at Dilia (is that how that city or town spelt?) where Nox helps Hannes (this is in the Hannes's diary Drama CD). Other than this there is no other interaction between the two of them yet. They might meet again but I will leave that alone until Zektbach fills the time gap between end BJ drama CD to chapter 8 and ending. Because the guidebook is jut giving the dot points of the chapters all the way to the end which he tends to do in advance and later slowly reveals more details and all.
However it is indeed stated in the guidebook that from that brief meeting between Nox and Hannes, both Nox and Hannes think each other existence bring great peace/tranquility to him/her.
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As far as I can speculate, I think there is definitely signs that Nox and Hannes is being each other 'love interest', the misleading part is the Ristaccia PV being no longer completely 'valid'
Many informations before the release of Turii Panta Rhei, is being made invalid/contradicting the new informations released on newer media. One of them is Nox cutting his hair. When the Zektbach twitter still active, the answer given when being asked about this was 'it will be told in the future'. Then in the guide book it is explained as 'the cutting of hair in the PV is the symbolism of Nox's despair' or something along that line.