Nagisa was your twin brother. Your dad wasn’t around and your mom was a controlling woman who tried to turn Nagisa into the girl she hoped he was. The both of you were in E class, the ‘failure class’. Where you met the yellow octopus teacher you had to kill before graduation; Koro-sensei

You got really close to assassinating Koro-sensei, but managing to cut two tentacles off which no one else managed to do yet

Woah! How did you do that?! I can’t even cut one off let alone two!