Ayashi No Ceres

Could someone tell me what the ending of Ayashi No Ceres means and what it’s all about? I mean, I’m quite lost even when I’m watching halfway (and probably everyway!) throughout the series. From the opening credits, you might think that this is a hentai anime, but it really isn’t. This is what I understand. Aya Mikage and her twin brother Aki are decendents of Ceres, a celestial maiden who came down from the heavens to take a bath in one of Earth’s streams (why would a celestial being do that? Isn’t the water in heaven heavenly?). But her robe was stolen by a mortal. So in order to get her robe back she was forced into marriage to this guy and thus bein the mixed blood relationship kind of thing. So fast forward to present day, unlike any other teenagers who gets presents or parties when they turn 16 on their birthday, Aya and Aki get a rude shock when they find out that their grandfather is trying to kill them. Why didn’t he do it much earlier? So we see Aya running here and there avoiding assassination bids after bids. Oh, did I mentioned that Aya can unwittingly transform herself into Ceres which have some super powers but she seems to want to keep her away too and not transform too frequently. But luckily she’s got a good pal-cum-protector Yuuhi to keep things at bay for awhile. Then I also understand her twin brother hoped onto the otherside of the bandwagon and joined his grandpa in hunting down and kill her own twin sister. This really brings family feud to a whole new level (but he sacrificed himself and died at the end). Also, there’s this guy, Tooya, at first was on Aya’s grandpa’s side, then later on, donno what happened, switch sides and becomes Aya’s other protector. Then the 2 became a couple and I think they got married at the end (because of Aya’s pregnant tummy, I assume). Err… so could anyone please tell me what is really going on and what this is all really about? Maybe I should watch this anime again, if they re-run it of course.