"Vita Sexualis" is Mori Ogai_s Naturalism novel. This work is made with the purpose of showing how naturalism themed novels should be made to Japan society especially Japanese naturalism writers. "Vita Sexualis" is a story about Shizuka Kanai_s sexual life from which he was six years old to 23 years old. Human male sexuality will be explained through Shizuka Kanai psychosexual development. Through analyzing every event that happens in Shizuka Kanai_s life through six years old to 23 years old especially events related to sex, the writer_s got to see that Shizuka Kanai has an asexual symptom in his latent phase and he left a fixation in his infantile-phallic phase which restraining perfection in his genital phase development.