I think it might be more like full scale war he wants her to avoid. There is a difference between fighting off 1-10 people and hundreds to thousands of people killing each other.
I'm thinking more like it's evolved to 8-tails and then some kind of trigger (shady deal with demons, empowering medicine, etc....) will give it a temporary 9th tail.
I missed that as well. I was so confused when I saw it this chapter.
Edit: Went back and checked. Chapter 10 is when it's show. I do not remember it at all.
We don't actually see Celes/Celestia's forehead, where the gem would be, so we don't know if she has one or not.
She also first appeared in ch 57 but we don't see much of what she looks like.
I'm really hoping we see the designs of all the other dragons that he didn't evolve into. Some of these sound so cool.
Also: These are A ranked dragons and sound devastatingly strong. What are S ranked dragons like?
I mentioned in the last chapter that I think it's the Dark Elves somehow controlling them. Because the monsters only when into a frenzy state AFTER he mentioned they were looking for them.
I went back and checked; I didn't see anything about "love" being emphasized as part of it. Rather they might want to do it with someone they like than just a rando.
If a strap-on was usable then so would be a dildo. If that was all that was needed, then there wouldn't be a huge deal about finding a partner. It probably has to be the opposite genders genitalia (and maybe juices) for it to work.
Sure, he has no public reputation, but he was scouted by THE S-ranker and the Guildmaster. That would surely make them think maybe there is something more to the MC.