Thirty seven year old Satoru Mikami may be a typical corporate worker, who is perfectly content together with his monotonous lifestyle in Tokyo, aside from failing to nail down a girlfriend even once throughout his life. within the midst of an off-the-cuff encounter together with his colleague, he falls victim to a random assailant on the streets and is stabbed. However, while succumbing to his injuries, a peculiar voice echoes in his mind, and recites a bunch of commands which the dying man cannot add up of.
When Satoru regains consciousness, he discovers that he has reincarnated as a goop of slime in an unfamiliar realm. In doing so, he acquires newfound skills notably, the facility to devour anything and mimic its appearance and skills . He then stumbles upon the sealed Catastrophe-level monster “Storm Dragon” Veldora who had been sealed away for the past 300 years for devastating a town to ashes. Sympathetic to his predicament, Satoru befriends him, promising to help in destroying the seal. In return, Veldora bestows upon him the name Rimuru Tempest to grant him divine protection.