Kinoko Nasu
The first seven of these stories were written by Kinoko Nasu like the rest of Kagetsu Tohya, while the last three are contribution works by others, essentially fanfiction. It is unknown if any of these stories are to be considered canon. In fact, some are obviously NOT canon, such as Imogirisou and Ciel-Sensei. It is likely, however, that the background information is to be considered canon. (Such as Nanako-chan and Arihiko's pasts, along with the explanations for certain plot holes in Ciel-sensei, such as how Chaos and Arcueid got to Japan).