I have to admit this was an interesting and informative episode. After going what 23 episodes later. It was certainly good to see 'Mai' and 'Mikoto' again. Gotta love "feral" girls.
Well, so far I was somewhat on the mark. Especially about the princess and the gem. The only thing that was still the question was who the real princess was. But after watching the episode I was a little confused until I ran it around in my head again. It was mainly about the gemstone. I was trying to figure out how the gem got back in 'Arika's hand even though 'Miyu' mentioned it. Then I realized the confusion came from all the "bones" that Sunrise was throwing to keep people guessing. Just to end up back to what we had suspected all along. Then again the 2nd OP also give you a clue. The 2 scenes. The one where 'Arika' is wearing the blue robe and when 'Rena' fades to 'Arika'. Which can be interpreted as "successor" or "Rena's daughter.
To the person who quoted me awhile back, saying that the gem doesn't necessarily get passed down. And I have to agree on that. Back to the speculation I made earlier is that 'Rena' put the gem on the royal heir as identification. Because technically the gem goes back to the royal family. So they can choose one worth of being 'Rena's successor for the future royal family. But I had a lot of problems with this. Most of it has to do with 'Nina'.
Surise must have been trying to put way to much into getting this new season out, because there's enough "holes" for a 'Mack' truck to pass through.
First, if 'Nina' was the princess (that's if she is, I don't trust Sunrise) where the hell did she end up? From what we can see now there was only 1 capsule. When 'Rena' sent the princess off to safety. So of course she expected that she would be found and make it's way back safely. Apparently, that didn't end up being the case. Someone found it. Miyu found 'Arika' as she stated.
Now think about this for a second, don't you think that whoever found the capsule would have known that it wasn't ordinary? It's ornate enough. And if they looked inside, and saw there was a baby with a gem on common sense would tell that person that this is no ordinary baby. Lowlifes or regulars are not that stupid to not know that this child is special. And with the buzz going around...c'mon! Yet the gem was stolen and being sold in 'Artai'. Which is where 'Miyu' found and retrieved it. My thoughts are they wanted the gem. Having a child in your custody would cause too much notice and too much trouble. Especially, when you have royal forces out looking for it. Either leave it where it is, let someone else deal with it or dump it somewhere else.
Second, how did Nina' end up in the underground bunker for assassin trainers? We know this because it's one of her earliest memories that she remembers the most
(ep. 11, HAPPY☆BIRTHDAY). The full info. doesn't come until later. Which is when 'Nagi' comes across documentation concerning the incident and 'Nina. And from the photos he notices the capsule and compares it with the photo of the Windbloom's royal family. If it was a DNA test, it would be a 100% match.
Do assassins normally train babies? 
It's a funny thought though I don't think they would take them in that young. I would gather that they are enlisting them from some place else. Considering the type of poverty on the streets of 'Artai', you either grab kids from an orphanage or off the streets. "Want to eat, earn it when you learn to kill." From that scene in ep. 11 it makes me wonder if 'Nina' was ever in an orphanage or living the life of a "street rat". Back to the bunker
Now, if 'Nina' remember's being in the bunker why doesn't she remember the capsule? If that area was her own personal space then she had to remember that the capsule would have some answers to her past that she would have to unlock. But never once is it mentioned. 'Nina', never once questions further about her past. Who her father or her mother was. Even if she considered the capsule an important possession she would still recall it and wonder where it came from and where she came from. Even with 'Arika's blabbing about finding her mother triggers nothing in 'Nina' other than 'Arika' being 'Rena's successor and a "home-wrecker". But all that has been bypassed for 'Mr. Sergay'. "As long he's at my side I don't need anyone else." Hmmm, this is why you have friends to TALK THINGS OUT! "Don't need friends if I have to kill them one day." Now this is causing a conflict. You love and care about your rival. And deep down inside you really DON'T want to do what it is you're doing. As far as the "father-complex", well...I think that went deeper anyway. Surely, many remember 'Nemo' and 'Electra'
(Nadia).
As for 'Mashiro' she will probably end up being the last piece of the puzzle. I would put my bet on her having a connection to 'Fumi' the way her counterpart did in 'MH'. But I wonder if anyone an 'otome' chooses can be a master. That's something to think about. If 'Mikoto' could swallow 'Mai's gem and still make a contract because she's the 'Crystal Princess', then what was the reason why 'Mashiro' was able to make a contract with 'Arika'. What are the rules? Can a ordinary person be a master or does this only apply to those of royal ties? If so then 'Mashiro' has to be someone of importance. If she isn't of royal blood then she may have that "something" that overrides the rule. Just because she may not be the princess doesn't mean that she can't *BE one. I'm sort of looking into 'Miyu's words.
As far a blog I read about 'Arika' and 'Nina' not changing so much. In a way they did a bit. It's just that on the surface they're acting out their "original" ideals. While 'Arika' was too quick at the chance of being a 'otome' she had to mull over some situations and decisions. This was what Miss Maria was trying to drill into peoples heads. That being an 'otome' is not an easy decision. And once you become one there's no turning back. Mashiro is the only one that really showed bigger growth. So the only thing left to do is try and help 'Nina'. 'Nina' is really having a hard time. And if you really look at it she sort of chose being an 'otome' for the wrong reason too. Now that she's become on under bad circumstances she now feels a heavier burden. But is still willing to carry out what has to be done whether it might be right or wrong. Remember, an 'otome's job is to serve. Surely, we remember 'Fia'. Again, something else Miss Maria was trying to point out. Yes, she goes a little overboard, but hey blame Sunrise for writing the character this way. But in reality she is a very tragic character. Because even she doesn't know what to do anymore than follow through with 'Nagi's plan if that will make things better. So she's really psychologically messed up. And having all that power doesn't make it any better. The irony lies in the 2nd OP. Windbloom's princess -vs-Windbloom's otome.
As far as the 'MH' connection. Too much info. for me to fathom or even care about.
Well, I guess that my 30 cents. I wanted to sort of get this off my chest because it was eating at me during dinner-time. Hopefully, ep. 24 will have some more answers. Then 25-26 back-to-back if that's true. Of course I'll be away when that happens.
Artist
oh! and is it only miyu can see arika's golden hair?
Bankai, maybe. 
)
YAY~!! and ARRRGH
... well this is just a guess 
