I really outta read up on Ciel, since I didn't bother once I knew it wouldn't make it over, but hearing that it's a sim makes me wonder if it's anything like Princess Maker. PM2 was the shit, man...
From my understanding (as somebody who hasn't actually played the game but has at least researched it and watched some gameplay vids at least), I think it's better to just think of Ciel as a VN with a somewhat unusual presentation. The whole idea is that you're not playing a character, but rather interacting with Ion directly through some kind of terminal that connects you to her world (in other words, your Vita...bet you didn't know it could do that). Ion is living in this crazy dream world and her memories are a complete mess, so the real goal is to help reconstruct her memories and figure out what the heck happened to her.
There's a whole online/social element to the game too, but it sounds like that's being taken out entirely for the offline version. Which I'm totally OK with ;)
In Ar Nosurge Ion has gotten her memories back and is one of the main characters in the game. And let's just say that the shit that happened to her--which you're supposed to know already from playing Ciel--is pretty friggin important in Ar. Sure you can try to piece things together, as I kind of did, but I really wish I played Ciel first now...that's why I'm upset that they're not even localizing Ciel.
TK America's twitter account confirmed that Ar Nosurge will be coming to the US as well. Details will come later.