i decided to check the autor page on X, its odd after it was finished the autor did not make any more art of the series, ".
So essentially, they told him the axe was falling and gave him the choice of how to conclude it.
I'm back after awhile and wanted to add some details from looking around. Prepare for a big yap.
All three commentators give good points on both sides and definitely more through than my theory on what thematically would make sense and matter more for the ending of the series.
What I've gathered is basically that the ending is open ended and the author doesn't like readers asking too many specifics (based on twitter replies). The author has actually posted a few art(like 1 or 2) after the end of Volume 3 but nothing crazy or important. I wanted to add the author's intention with the story based on his Twitter replys was to relato it to miya-chan mother. Her mother was a succubus that slept around a lot until her father "tamed" her and she betrayed/gave up being a succubus for him because she valued his love. The author said he wanted a similar premise with Miya herself and onodera and if he could continue the series that's what the plan was.
This again supports both ideas, 1 maybe she did sleep with tan playboy kun and she started sleeping with oji and many more, then onodera would slowly convince her to stop with love or something.
Or 2) Based on the author saying the idea was a similar idea to her mother not the exact same; then miya was doing dream sex and getting addicted to it till onodera saves her with love or something and takes her first time likely.
Both are about equally likey.
I personally agree with the commentor who can understand Japanese and broke down the meaning but I appreciate the guy who gave a through reasoning on his view as well as I'm also a yapper. I gave my reasons a lot earlier on why I personally think thematically the author was pointing to option 2 for the main story ending so I don't think she actually had sex. I disagree with the people that comment saying the author just planned on having an ntr work so she banged and that's it, besides for ch1-2 and ch 17 their isn't much ntr for miya as onodera is a big side character till last chapter (that one beach guy sister did get ntrd tho lol). A ntr authors and works usually have constant ntr if its the focus like grapara or guilty circle. I also don't think the end goal was Miya loosing her virginity (which is another reason why she didn't imo in chapter 17. Also the roses in fireworks scene usually mean she's using her powers or a dream is starting/ending like other commentor mentioned), as the end goal of this series seems more focused on taking control of yourself based on miya mother and miya fate with onodera whether she slept around or not.
(Wanted to credit this guy reply also for his detailed interpretation on the translation. Meant to do it with the above comments that's why I said 3 commentators but did it too late on accident lol).
Hope this clears things up!
But the final point is it's obviously open ended if she fucked or not to put it simple. Because of the axe it basically ruined and would rushed the ending so the author very blatantly doesn't want to make a clear cut ending for the readers as he's already disappointed it had to end this way to begin with. In situations like this I usually just ask the authors in Japanese they're thoughts and they'll give a vague answer (except the alice in cradle game dev they gave a clear cut answer when I asked about the fmc) and similarly with this work the author seems finished with it overall. The work could easily have wrapped up with one last volume is the real part that stings imo and seems the readers and author agree on that. Check his fantia from time to time as I think all posts are free and he posts an update occasionally every few months.
Although not sure if anyone even cares after mangadex gave the ban hammer... Rip.. At least it'll be useful info for future readers!