森の木の上に何か光るものを見つけた瞬間、その光が夏目の目の中に！何者かがやって来る気配と共に突風に襲われるが、居合わせた田沼がとっさに夏目をかばう。その翌日学校を休んで以降、何か夏目を避けているような様子の田沼が気になっていた夏目は、学校の裏庭でうずくまり穴を掘っている田沼の姿を目にする。やはり何かおかしいと田沼を追おうとすると、夏目の目に激痛が走る。

숲의 나무 위를 살펴보던 나츠메의 눈에 빛나는 뭔가가 들어간다. 순간 누군가가 다가오는 듯한 기척과 함께 돌풍이 불지만, 곁에 있던 타누마가 나츠메를 감싼다. 그 후 타누마는 감기에 걸렸다며 나츠메를 피해 다니고, 학교에서 흙을 파는 등 수상한 행동을 보인다. 그리고 타누마를 쫓던 나츠메의 눈이 아프기 시작한다.

夏目与猫老师外出寻找因雷击古树而出现的酒泉，却意外走散而遇到田沼。在森林之中田沼被妖怪附身，虽然在几天以后的学校中夏目发现了这一事实，但妖怪却要求夏目协助自己寻找自己镜子的碎片。于是夏目、田沼和多轨三人从校园中开始寻找碎片……

森林中，夏目發現樹上有什麼東西正在發亮，沒想到那個亮光竟然掉進夏目的眼裡。此時突然颳起一陣風，就在夏目眼看要被攻擊時，田沼幫夏目擋下了。隔天田沼沒來上學，之後夏目覺得田沼好像在躲他，而且他發現田沼竟然蹲在學校的庭園裡挖洞。夏目擔心地跟了上去，眼睛卻感到一陣劇痛…

An event in the forest causes Tanuma to avoid Natsume the following days, which he becomes concerned about. Mirrors are mysteriously breaking around the school and one day Natsume catches Tanuma acting weirdly. It turns out that Tanuma has been possessed by a youkai looking for her mirror, which had been broken into pieces during a storm a few days before. Using him as a vessel until she reclaims her mirror, Natsume has no choice but to help her. The youkai warns that there may be others seeking the mirror.