Satoru Mikami, a 37-year-old corporate worker living in Tokyo, is content with his mundane lifestyle, save for his inability to find a girlfriend. One day, while chatting with a colleague on the street, he is attacked by a random assailant and fatally wounded. As he lies dying, a strange voice speaks in his mind, issuing a series of incomprehensible commands. When Satoru awakens, he finds himself reincarnated as a shape-shifting slime in an unfamiliar world. With his new abilities, he comes across Veldora, a powerful monster who has been sealed away for three centuries. Satoru promises to help Veldora break the seal, and in return gains divine protection and a new name - Rimuru Tempest. Now free to explore this new world, Rimuru begins a journey with a clear objective in mind. As he becomes more comfortable with his abilities, his actions start to have ripple effects throughout the world and alter his fate.