Gust usually extends their games with downloadable content. The Atelier games for PlayStation 3 have additional characters and dungeons, but after a few months the extra content tapers off. But, not for Ciel no Surge.
Later this month, World Pack Vol. 5 will be available for Ciel no Surge. This adds a free talk pack with Ion where you can take her on a date in a church.
You can also get additional costumes like these overalls and accessories for the Sharl. The costume pack which has Dragon Horns, Goat Horns, and a red cap (that looks like a belated Santa hat) costs 300 yen.