Yurei Gakkou Kyoufu Nikki

I change schools every year due to my father's work. Whenever I go to a new school, I am always filled with hope and anxiety. However, the school I transferred to this time seems especially gloomy. My teacher tells me not to make friends with anyone and to stay away from other people.. Why in the world would my teacher say something like that? (Source: Sukima, translated)