"Sadamitsu the Destroyer" is a science fiction anime series that blends action, comedy, and supernatural elements. The story centers on Sadamitsu, a high school student who inadvertently becomes the host for a powerful alien entity known as the Destroyer. This entity grants Sadamitsu immense strength and destructive capabilities, but it also comes with a catch: the Destroyer has a mischievous and chaotic personality, often taking control of Sadamitsu's body to wreak havoc. The series explores the tension between Sadamitsu's desire to live a normal life and the unpredictable nature of the Destroyer, which frequently lands him in trouble.

The narrative unfolds as Sadamitsu navigates the challenges of his dual existence. On one hand, he tries to maintain his relationships with friends and family, including his childhood friend, Shizuka, who is unaware of his secret. On the other hand, he must contend with various adversaries, ranging from rival aliens to government agents, all of whom seek to exploit or eliminate the Destroyer. The series balances episodic adventures with an overarching plot, as Sadamitsu gradually uncovers the origins of the Destroyer and its connection to a larger intergalactic conflict.

Key characters include Sadamitsu's classmates, who often find themselves caught up in his supernatural escapades, and a mysterious organization that monitors extraterrestrial activity on Earth. The dynamic between Sadamitsu and the Destroyer is central to the story, with the latter's unpredictable behavior serving as both a source of comedic relief and a driving force for the plot. The series also delves into themes of identity, responsibility, and the consequences of wielding great power, as Sadamitsu struggles to reconcile his humanity with the destructive potential of the alien entity within him.