Aboutに情報を追加するためにゲームのレーティングを再確認しましたが、アルノサージュ英語版は１３歳以上の指定なんですね。そんなに大きい変更箇所は今の所見当たりませんが…むしろどこでオリジナルがCERO Dになったのかが疑問。過激度でいえば、禊よりアルトネリコ３（CERO C）のパージの方が上の気も。
アルトネリコは設定資料集のインタビューでレーティングについての説明がありましたが、サージュはそういう機会がなかったですよね…。Dなのに、成人設定のデルタとキャスが普通にキスもしないのは逆に不自然に感じるし（ディズニー映画でもしてるのに）。謎です。
I rechecked rating of the games to add information into About page, then I noticed English version of Ar nosurge was rated as TEEN. Currently, I haven't seen that many modified points, though. I rather wonder what did make the original version as CERO D (for over 17 years old). If you talk about extreme expression, I think Purge in Ar tonelico 3 (rated as CERO C, for over 15 years old) is more radical than Purification.
There were explanation about rating of Ar tonelico series in interviews included in Setting Reference Books, but we haven't got such opportunity for Surge Concerto series, have we? I feel it's unnatural that Delta and Cass who are supposed to be adults don't even kiss on the mouth (characters do it even in Disney movies!). It's a mystery.
※後日追記
*Additional Notes
上記のことですが、やはり「キャスが幼く見えること」がネックなんだと思います。日本とは違い、欧米では設定上何歳であろうとキャラがどう見えるかが判断基準です。（日本のアダルトゲームでよくある、明らかに子供の外見のキャラがいても「登場人物は全て18歳以上です」は通用しません。）英語版前提で性的な行為を表現するわけにはいかなかったのでしょう。キャス、ネイ、サーリは外見が変わらない理由が作中で説明されていて、キャス自身もそれについて不便な思いを語る会話があったりしますが、アルノサージュの初期案段階ではキャスも普通に大人になっている想定でした（画集THE FINDERより）。設定上で辻褄を合わせることは可能でも、そこまでしてキャスの外見を幼いままにする必要性は本当にあったのだろうか？と、私個人はやや穿った見方をせざるを得ません。
About the question above, I think that the fact Cass looks young is the bottleneck after all. Unlike Japan, this kind of decision in Europe and the United States is made basing on how the character looks, not how old is she in the setting. (Even if there is a character which obviously looks a little kid, it is common in Japanese AO-rated games to make an excuse with a message "All characters are over 18 years old". That is not the case in foreign countries.) I suppose sexual expression couldn't be included since it was not allowed for English version. Within the game, the reason why appearence of Cass, Nay, and Sarly does not change is explained, and Cass herself talks about inconvenience about that. However, in the early draft stage of Ar nosurge, Cass was assumed to be a normal adult (from the illustration book "THE FINDER"). Was it really necessary to keep Cass' appearance young even though it could be made plausible by the setting? Personally, I can't help to take a slightly distorted view.
