Available from Mangagamer, Cartagra is the first title from publisher Innocent Grey, also responsible for Kara no Shoujo, to which it bears many similarities.
This review will contain spoilers.
Cartagra is Innocent Grey’s first title, and as such I can’t really help but compare it to Kara no Shoujo. It has many similarities, and even shares some characters, but ultimately it’s a less polished affair. That’s not, however, to say that it’s bad. Far from it.
I did my first playthrough blind and then used this guide to unlock all the other endings.