Inuyashiki

Ichiro Inuyashiki is an elderly guy with no friends and a heartless family. He is struck by an explosion of extraterrestrial origin one fateful evening in a largely deserted public park, and his body is replaced with an extraordinarily strong, albeit externally still human, mechanical body. After saving a homeless guy from being beaten by a group of youths after he soon understands the depth of his body's talents, he resolves to dedicate his life to doing good by utilizing his abilities to treat people with terminal illnesses and fight crime. Shishigami Hiro, a teen who was present when the explosion occurred, suffered the same fate as Ichiro, but unlike Inuyashiki, Shishigami turns into a psychopath and begins killing people for enjoyment, including innocent families with young children and bothersome classmates. The police are called to him because of his heinous crimes, but they are powerless to stop him. Hiro becomes the nation's most wanted criminal. The show focuses on the collision of these two disparate characters who once had the same unusual event.