Rinacoladaaa
After Koro-sensei's death, Nagisa Shiota chose a path that defied everything his teacher stood for, except one promise. "I will use my stretch to protect others."
Now a professional assassin, Nagisa lives a double life, respected teacher by day, cold executioner by night. Though guilt haunts him for using the very skills he once promised to abandon, he justifies every kill with a single belief. The world is better off without certain people.
He bears the burden of each life taken, shouldering the darkness so others won't have to. But as he delves deeper into the underworld, Nagisa discovers he may not be the only one from Class 3-E who chose a violent path. Shadows of the past begin to resurface, and with them, secrets that were never meant to be uncovered.
Assassination classroom after story where Nagisa chose to become an assassin rather than a teacher. Cause I just watched Assassination classroom.