Genomu hazâdo: Aru tensai kagakusha no 5-kakan

Ishigami comes home from work and discovers his wife dead. Just then, he receives a phone call from his wife and falls in utter confusion. Unexplainable things keep happening as Ishigami struggles to find his wife. Gradually, Ishigami realizes all his memories are gone and finds himself acting like someone else. What is his true identity?