I seriously just wrote a mile long post and magically closed the window because I'm a retard. So for now I'm only reanswering a couple because I'm ANGRY!!!

april6e wrote:

1. Anthy is Mimiya? Can you explain why this is?

4. Who is Dios? Who is that person who "possesses" Utena so that she wins her duels? It looks like Mamiya but isn't Mamiya dead? And he looks nothing like Akio.

These two kinda relate to each other.

Anthy is Mamiya based on this sequence at the end of the arc:




Also it follows based on Mamiya in the present looking strangely like a female Anthy. As to WHY, well it would appear to have given Akio and Anthy a manipulative advantage to have Mikage controlled directly by such an influential shadow of his past.

The REAL Mamiya is dead. The real Mamiya is the brown haired boy that appears during Mikage's duel. Mikage has so accepted the illusion of the Mamiya we see at the present that he's forgotten what Mamiya originally looked like. That's why the flashbacks initially show the brown skinned boy--Mikage remembers it that way. The photograph on the desks during his duel changes as his 'remembers', starting with this:



And turning into this:



As this processes in his mind, you also see how his memories revert to their original truth, the Mamiya of his present being replaced/recalled to be the original:





The real Mamiya is dead. This is why Tokiko comes, literally, to visit his grave. (That she makes a pit stop at Akio's is...suspicious, for a presumably happily married woman.)

As for the Dios thing, he looks like Akio in that he has dark skin and silver hair and their outfits kind of match. The dark skin color is a big red flag in this show, since only the supernatural magic wonder siblings Akio and Anthy have it--any other time you see that skin, it's actually one of them presenting themselves differently. The Dios Utena meets in her past is Akio presenting himself as the prince part of him that's long since died. The Dios that helps Utena win her duels...well that's up to you. The show doesn't really say whether he's part of Akio's projection of the arena, magic on Anthy's part, or the real deal embodied in Utena and manifesting visually. It doesn't even really confirm if anyone else sees the figure--Touga and Ruka both make an effort to observe whatever happens to Utena that makes her keep winning, but they don't say they saw some dude fly down and take over Utena's body.

april6e wrote:

5. Some people claim that Akio creates illusions with his projector. While an amazing analysis, how does that explain Utena's "possession" moments where Dios helps her win duels?

Akio claims he creates illusions with his projector in the second to last episode, which is where we get that. He could be completely full of crap and it wouldn't be the first time. Aside from that comment the show doesn't give you more to stand on directly there. He could be telling the truth, or he could not need it at all and just like the symbol. He could need Anthy's power to draw from, and just have the ability to give it form. In the end, that detail is up to the viewer. Convincing arguments can be made from several sides.

Furthermore, we aren't told directly that the the possession moments are part of the illusion. That's also for you to decide--it is worth noting however that what goes on in the arena isn't only Akio's to decide. His arc begins with the sword of Dios vanishing--and not on his authority, given his reaction.

Your question 4 seems to kinda crash the movie and show together. Utena's prince is Dios in the show, and has nothing to do with the drowning girl. That's the movie.

And I'm not sure who you're asking about with the sexual relationships--I don't think anyone assumes Touga and Saionji actually have sex. We assume Akio and Touga do just because it so makes sense given their personalities. Also, this shot looks so obviously like a man riding another man's lap that it's hard to assume we're not supposed to see it that way.