Second season of Mato Seihei no Slave.

The tropical Seiren Island is a paradise for deviants: the infamous Pervert Law grants near-complete sexual freedom with almost no taboos or boundaries. With its various suggestive attractions, the Seirantou Health Organization (SHO) entices visitors while providing regular medical checks and contraceptive pills to ensure carefree enjoyment. However, for high school student Junnosuke Tachibana, the island is far from ideal. Having recently moved there with his younger sister, Asane, he cannot stand the empty, loveless sexual acts. To make matters worse, Junnosuke's abstinence attracts unwanted attention—and those who defy the law face punishment. Junnosuke soon crosses paths with Nanase Katagiri, a notorious island seductress. Surprisingly, instead of forcing herself on him, she helps him flee from the SHO. Together, they discover a secret group that exists for a singular goal: to destroy the SHO. Now equipped with a way to resist the unjust rules, Junnosuke and other kindred spirits set out to crush the Pervert Law.

After the demise of the demon king, the resulting power vacuum has broken the balance of the world. Eager to claim this power for themselves, self-proclaimed demon kings from various worlds assemble in the New Principality of Lithia to fight for it. Among them, master swordsman Soujirou Yagyuu seeks to take this coveted position for himself. Joined by Tooi Kagizume no Yuno, a young girl he saved from an army of golems that destroyed her city, Soujirou enters Lithia to battle his way to the title. At the same time, the leaders of the Aureatia Kingdom seek to destabilize Lithia by launching bandits after the convoys of merchandise transiting through the principality. Enraged, Imashime of Taren, the founder of Lithia and defector from Aureatia, sends vicious thief Kasasagi no Dakai to investigate the origin of these attacks. With war on the brink of eruption, no one can predict what influence the contenders for the demon king's throne will have on the coming conflict.

The battle against the forces of evil is nearing its end as the Undead King Leonis Death Magnus remains the sole survivor of the Dark Lords. Standing no chance alone against his enemies, Leonis seals himself deep underground with the goal of reincarnating a thousand years later and rebuilding his demonic army. Within the span of a millennium, however, everything has changed. People no longer remember the great war that led to Leonis' defeat and instead face a new threat—the monstrous creatures known as Voids. Magical devices have replaced sorcery, and humans with special powers—manifested in the form of weapons called Holy Swords—train at the Excalibur Academy to fight the Voids. Reborn as a 10-year-old human boy, Leonis meets Riselia Ray Crystalia, a dutiful girl who stumbles upon the ruins of his hibernation chamber. Believing that Leonis has amnesia, Riselia offers him guidance and enrolls him at the Excalibur Academy. Leonis still intends to take over the world, but he must first familiarize himself with a reality completely different from all he knows.