Go Nen Rei Gumi Kowai Mono Gakari 4 (Kadokawa Tsubasa Bunko)

[Machine Translation] A child who steps on the 13th step of a riddle staircase, which was supposed to be 12 steps, goes missing... That is the legend of the "cursed staircase. And this curse moves to other buildings. Scary! One day, a student disappears at Asahi Elementary School. And Hana-chan began to suffer terribly. She said, "Something very evil came to school. No way! The curse of the 13th staircase! What did Haru, the scary thing officer, see when she went to confront it together with Dokupan and Kagamiko? From elementary school intermediate level.

12段のはずの階段に現れたナゾの13段めをふんだ子は、行方不明になってしまう...それが「呪いの階段」の伝説。しかもこの呪い、ほかの建物に移動していくんだって。怖っ!ある日、あさひ小で生徒が消える事件が発生。さらに花ちゃんがひどく苦しみだしたの。「すごく邪悪なものが学校にやってきた」って...まさか13階段の呪いが!?ドクパン、鏡子さんといっしょに立ちむかった、こわいもの係・春の見たものは!?小学中級から。