My name is Suzume, a 17-year-old high school student. I live happily in a quiet town in Kyushu. One day, a young stranger asked me, "Are there any abandoned buildings around here?". He, Sota-san, has been traveling around looking for "doors" in places where people had disappeared. I followed him and found an old door in a ruin in the mountains. Remembering his words, I reached for the door...