Jigoku Sensei Nube: Kyoufu no Natsuyasumi!! Ayashi no Umi no Densetsu!

A summer trip takes Nube and his students to a small island, where an old resident warns them about a terrifying legend: a sea spider that becomes a man-eating monster after living for two centuries. The story sounds like another local superstition until Yukime decides to investigate it for herself.

Soon, a mysterious girl appears on the beach and captivates Hiroshi, while Kyoko and Ritsuko are attacked under increasingly strange circumstances. As the incidents begin to match the old warning, Nube must uncover the girl's true nature and confront the supernatural danger lurking beneath the island's peaceful waters.