Kono Danshi, Sekka ni Nayandemasu.

Ayumu Tamari suffers from Crystallization Syndrome, which turns parts of his body into immobile crystal whenever stress overwhelms him. Severe social anxiety causes attacks so often that he repeats a year of high school and becomes almost unable to speak with his classmates.

His greatest comfort is homeroom teacher Kouya Onihara, a collector fascinated by the beauty of Ayumu's condition. The attention offers safety but also creates emotions neither can address easily, forcing Ayumu to confront his fear of others before the pressure causes him to crystallize completely.