Anthy sealed Dios away by offering to take all of the pain that Dios was receiving from the world... "The Rose Bride takes the swords in place of the prince"... Dios became corrupted by no longer having any of the pain of being the world's prince, and instead he became "End of the World". He says he's no longer the prince that Anthy cared about, and yet, Anthy continues to take all the world's punishment in place of him... Since Anthy is continuing to suffer as a witch for Akio's sake, even though Akio no longer qualifies as her prince.. He feels that Anthy must enjoy being this way... that Anthy is letting him use her out of her own free will. So in that case, what is it that Akio could want?
Even though Anthy is the one who sealed away Dios and the power to revolutionize the world, it's clear that Akio and Anthy can not access this power on their own... They need a duelist who has reached duel of revolution. I theorized before that this restriction was Akio's or Anthy's doing.. maybe it's due to Anthy's subconcious effect on Dios's power, or maybe the "good" side of Dios placed this restriction on his power so that only a good and noble prince can use it... But anyway Akio and Anthy are able to show people a glimpse of eternity and manipulate them into dueling to make the Rose Gate appear. This is what Akio did with Utena when she was little.. he showed her "eternity", and that lead her to becoming a duelist.
Later in the series, Utena can no longer draw out the sword of Dios from Anthy, for reasons that are never explained... I think it's because Akio didn't want Utena to be the one to open the Rose Gate. He wanted to do it himself, using Utena's sword. He must have already tried and failed to open the Rose Gate using the sword of Dios, so he figured he needed another prince's sword. From then on, Anthy draws out the sword from Utena in all of her duels. In the final duel, it's Akio who draws out the sword from Utena, and doing this turns Utena into a princess... I guess that Akio taking Utena's sword boosted his own princely image, and made Utena take on the form of a princess (it doesn't need to have more meaning than that really)...
Even though Anthy is the one who sealed away Dios and the power to revolutionize the world, it's clear that Akio and Anthy can not access this power on their own... They need a duelist who has reached duel of revolution. I theorized before that this restriction was Akio's or Anthy's doing.. maybe it's due to Anthy's subconcious effect on Dios's power, or maybe the "good" side of Dios placed this restriction on his power so that only a good and noble prince can use it... But anyway Akio and Anthy are able to show people a glimpse of eternity and manipulate them into dueling to make the Rose Gate appear. This is what Akio did with Utena when she was little.. he showed her "eternity", and that lead her to becoming a duelist.
Later in the series, Utena can no longer draw out the sword of Dios from Anthy, for reasons that are never explained... I think it's because Akio didn't want Utena to be the one to open the Rose Gate. He wanted to do it himself, using Utena's sword. He must have already tried and failed to open the Rose Gate using the sword of Dios, so he figured he needed another prince's sword. From then on, Anthy draws out the sword from Utena in all of her duels. In the final duel, it's Akio who draws out the sword from Utena, and doing this turns Utena into a princess... I guess that Akio taking Utena's sword boosted his own princely image, and made Utena take on the form of a princess (it doesn't need to have more meaning than that really)...