Koro Sensei is a fictional character from the manga and anime series Assassination Classroom. He is an octopus-like creature with superhuman abilities, including incredible speed and regeneration. Koro Sensei becomes the teacher of Class 3-E, a group of misfit students, and offers them a unique challenge: they must assassinate him before the end of the school year to prevent the destruction of Earth. Despite his role as a target, Koro Sensei is a caring and supportive mentor. He helps his students improve academically and personally, teaching them valuable life lessons. His character blends humor, action, and emotional depth, making him a memorable figure in the series.