Synopsis
Ayumu Tamari has "Crystallization Syndrome," a condition where high stress causes parts of his body to crystallize, making movement extremely difficult. His severe social anxiety prevents him from speaking to any classmates, leading to such frequent crystallization that he must repeat a year of high school. His only comfort is his homeroom teacher, Kouya Onihara, whom he calls "Oni-chan Sensei." Kouya, a collector and researcher of crystals, finds Ayumu's crystal formations beautiful and intriguing. School stress combined with the complications of a forbidden student-teacher relationship forces Ayumu to seek normalcy while managing his emotions to avoid complete crystallization.