ThesaArt

First of all, to get that out of the way - yes, the translation is accurate. I double and triple checked to make sure the Japanese version says the same, and it's fully unambiguous too, so it's not like someone translated this line wearing fujoglasses or something. (The translation I'm using here is the one by @/Hisana on Youtube, all of their RGGO translations are very well done.)

Anyway, as we know, this RGGO story is about their (in RGGO) first bar outing. They drink together, we get a timeskip, Mine tells Daigo a random story that makes him laugh, and then Daigo hits Mine with this:

It's a 180° change in topic - nothing leads up to Daigo suddenly inquiring about Mine's personal life. While that part can be explained by a boss just wanting to get to know their subordinate better, if you really want to see it like that, the way Daigo goes about it definitely can't be. It's even more evident if we look at the Japanese line:

The とか at the end of the phrase signalizes that Daigo is inquiring about a relationship partner (gender neutral btw!) as one of many things Mine could potentially have going on in his private life. But why is this the first thing Daigo's mind goes to, if he just wanted to know Mine better? What about asking about his hobbies, favorite foods, friends and family? The fact that he asks about neither of those, jumping straight to a potential relationship partner, makes the とか…… suddenly feel like Daigo is trying to sound casual and nonchalant about what is a very obvious advance on Mine to everyone with eyes.

(What's more, 交際している相手 carries the light nuance of someone Mine is currently dating. It may not make a huge difference, but it is worth noting Daigo is inquiring about Mine's current dating life, where instead he could be asking about stable relationships like marriage if the idea was just to get to know his subordinate better.) And it does seemingly strike Mine as odd, reacting to the inquiry dumbfounded if not flustered.

And then, of course, the biggest giveaway to me that this scene was intentionally written with romantic subtext is the fact it then gets interrupted by Daigo's phone.

Which is, like, the oldest trick in the book of romance media - interrupting a tense moment that could lead to certain romantic developments, especially with phone calls lol. If Daigo's inquiry was supposed to be a casual conversation between friends, there would be no reason to interrupt this moment. And actually, we have proof for that in Dark Ties!

Funnily enough, I've seen people trying to discredit the Daigo scene using this moment in Dark Ties, because "Kanda asked about Mine's relationship status too though!!" I think it's obvious that the context of these moments is very different though (Kanda has a reason to breach this topic because they're in a soapland, and he's clearly doing it for horny reasons because he wants to talk about girls with Mine lmao), and I'd go even further: I think this scene further proves the romantic nature of Daigo's inquiry. The reason is simple: Mine doesn't react uncertain or flustered to Kanda's question. He gives a straight answer to the question, and the scene doesn't get interrupted by anything either. There's no buildup nor tension, no phone calls interrupting Mine's reply. The "new scenario" of Dark Ties, which I'm pretty sure includes the Kanda Bro Time scenes as they don't really count as side content (imo), is written by Takeuchi according to the DT credits. Takeuchi also wrote the Daigo/Mine character story from RGGO, as far as I'm aware. It's the same writer portraying similar scenarios very differently depending on who's the one asking Mine the question, and I can't help but feel this was intentional on his side. (It's also worth noting that this same Kanda Bro Time event pretty much confirms Mine being gay. So I wouldn't be surprised if these two scenes were written to go along with each other.) There's more to be said about the context of this line within the full RGGO story - like how I think the full story reads like a classic romance drama plot that hinges on Mine recognizing Daigo's flirting (and thus growing rightfully suspicious of him allegedly meeting with a woman, or how Daigo leaving with a woman could be read as a subtle call for help to Mine to signalize he's in trouble, since he couldn't talk about it). But I think that part is a bit more open to interpretation, and since this post is already getting long, I wanted to focus on what's actually textually there.