Ode to Kirihito (2006)

English translation of the Japanese manga Kirihito Sanka.
Kirihito Osanai is a young doctor who's just been introduced to the Monmow disease, which transforms humans into dog-like beasts and kills them within a month of the metamorphosis. While studying the pathology of the disease Kirihito himself becomes an unknowing guinea pig for his hospital's research into it. Under the auspices of research, Kirihito is sent to a remote village in the mountains, where he contracts the Monmow disease himself, and through a series of misfortunes, becomes estranged from his beautiful fiancee, Izumi Yoshinaga (the daughter of his hospital's Director and Chief Physician), and his close friend and rival, Urabe.