For all we know she's embarrassed about masturbating at home so had to go crazy solo at the hotel
You know, after taking a step back from this and just not giving a fuck any more, this could actually be true.
Right now I think the safest route that Suga could take right now is going down a path like that, and some of the previous chapters lend some credence to the idea.
We've seen it in previous chapters that ever since Naoto caught Luna masturbating, every other time we know of it happening
is when he's not home. Like the chapter where he forgot his wallet, Luna waited for Naoto to leave the apartment before she started.
It's entirely possible that she got so worked up that she had no choice but to find somewhere else to do it, otherwise Naoto would catch her again and make things even more embarrassing, or she was getting to the point of actually attacking him.
This would also make sense as to why she went to a normal hotel, as opposed to a love hotel if she was just meeting someone for a fling.
We also know that she had been drinking that night as well, and the dreaded door opening could have just been room service bringing her alcohol and not actually a person she was meeting with.
With all of that in mind and with the previously mentioned "they are like two ships passing in the dark" at the end of chapter 25, it's entirely possible that while Naoto thought that Luna went to the hotel to have sex, while she actually went there so Naoto wouldn't hear her again, especially when she has been thinking about him and calling out his name while doing it. This would also explain why she "couldn't face him right now", because she just spent the entire night masturbating while thinking about him.
Also going to point out that the app keeps getting called a "dating app" instead of a
matching app, which is making things sound a whole lot worse than they possibly are. As it was pointed out by Mimi previously that the app isn't used just for dating or sex, but also to meet new people and friends (
we also see that hers are also MEN).
While this doesn't really help much with the mess going on with the matching app right now, she just admitted to using it and didn't seem to directly relate it back to the hotel. Which leads me to believe that the person who Luna was talking to on the phone when she was looking after Naoto when he was sick, was someone she met on the matching app as the time frame fits into when
Hiba was overseas and Luna didn't have anyone around her and she got lonely. It's also possible that she met with that person again after telling them off, creating the weird dialogue at the start of the chapter.
Now at the end of the chapter, we see Luna seeming to act a bit weird, which makes me think that she may be getting ready to leave so Naoto can "use" the apartment (creating confusing) or we may be getting hit with another secret and she admits that she has been lusting after Naoto the entire time.
I'm hoping things actually go something like this, because the other options are looking pretty grim.